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- Committer: Package Import Robot
- Author(s): Jackson Doak
- Date: 2014-01-22 06:23:44 UTC
- mfrom: (5.1.6 sid)
- Revision ID: package-import@ubuntu.com-20140122062344-gdj5nf671oxprqq7
Tags: 4.1.2+dfsg-2ubuntu1
* Merge from Debian, remaining changes:
- Build-depend on libglew-dev rather than libglew1.5-dev | libglew1.4-dev
| libglew-dev.
- Build using -O1 on arm
- Build-depend on libglew-dev rather than libglew1.5-dev | libglew1.4-dev
| libglew-dev.
- Build using -O1 on arm
- files added:
- .pc/0001-Change-all-texinfo-variable-names-to-alpha-nums.patch
- .pc/0001-Change-all-texinfo-variable-names-to-alpha-nums.patch/doc
- .pc/0002-expand-homepage-macro.patch
- .pc/0002-expand-homepage-macro.patch/doc
- .pc/0003-Texinfo-5.1-workaround-disable-some-macros.patch
- .pc/0003-Texinfo-5.1-workaround-disable-some-macros.patch/doc
- .pc/0004-Texinfo-5.1-workaround-macro-on-a-separate-line.patch
- .pc/0004-Texinfo-5.1-workaround-macro-on-a-separate-line.patch/doc
- .pc/0005-Texinfo-5.1-workaround-macro-on-a-separate-line.patch
- .pc/0005-Texinfo-5.1-workaround-macro-on-a-separate-line.patch/doc
- .pc/0006-Texinfo-5.1-workaround-macro-on-a-separate-line.patch
- .pc/0006-Texinfo-5.1-workaround-macro-on-a-separate-line.patch/doc
- .pc/0007-Leave-TEXINPUTS-alone.patch
- .pc/0007-Leave-TEXINPUTS-alone.patch/doc
- .pc/0008-Texinfo-5.1-workaround-macro-on-a-separate-line.patch
- .pc/0008-Texinfo-5.1-workaround-macro-on-a-separate-line.patch/doc
- .pc/0009-Texinfo-5.1-workaround-equationW.patch
- .pc/0009-Texinfo-5.1-workaround-equationW.patch/doc
- CMakeModules
- src/layer_selection
- files removed:
- .pc/10_ftbfs-gold.diff
- .pc/11_ftbfs_boost1.46.1.diff
- .pc/11_ftbfs_boost1.46.1.diff/src
- .pc/15_texi_ids.diff
- .pc/15_texi_ids.diff/doc
- .pc/16_hardcodeurl.diff
- .pc/16_hardcodeurl.diff/doc
- .pc/17_fixinclude.diff
- .pc/17_fixinclude.diff/doc
- .pc/18_disablemacros.diff
- .pc/18_disablemacros.diff/doc
- .pc/19_classictimes.diff
- .pc/19_classictimes.diff/doc
- .pc/20_semilog.diff
- .pc/20_semilog.diff/doc
- .pc/21_inline_foo.diff
- .pc/21_inline_foo.diff/doc
- .pc/22_fixpdfbuild.diff
- .pc/22_fixpdfbuild.diff/doc
- .pc/23_perl5.18.diff
- .pc/23_perl5.18.diff/src
- include/vigra
- src/vigra_impex
- files modified:
- .pc/applied-patches
added
removed
.pc/0001-Change-all-texinfo-variable-names-to-alpha-nums.patch/doc/enfuse.texi
1
\input auxmac
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\input texinfo
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@c
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@c Header
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@c
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@c %**start of header
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@setfilename enfuse.info
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@include versenfuse.texi
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@settitle Fusing Multiple Images with Enfuse @value{VERSION}
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@include auxmac.texi
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@include varsenfuse.texi
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@include config-h.texi
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@set default-image-cache-cachesize 1024@dmn{MB}
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@set default-image-cache-blocksize 2048@dmn{KB}
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@c Define a new index for syntactic comments.
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@defcodeindex sc
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@c Define a new index for options.
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@defcodeindex op
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@c %**end of header
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@c
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@c Categorization for the GNU Info System
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@c
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@dircategory Individual utilities
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@direntry
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* enfuse: (enfuse). Fuse images using a multiresolution spline.
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@end direntry
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@c
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@c Summary Description and Copyright
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@c
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@copying
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This manual is for Enfuse (version @value{VERSION}, @value{UPDATED}),
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a program to merge different exposures of the same scene to produce an
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image that looks much like a tonemapped image.
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Copyright @copyright{} 2004--2012 @sc{Andrew Mihal}.
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@quotation
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the @acronym{GNU} Free Documentation License,
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Version 1.2 or any later version published by the Free Software
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Foundation; with no Invariant Sections, no Front-Cover Texts and no
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Back-Cover Texts. A copy of the license is included in the section
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entitled ``@acronym{GNU} Free Documentation License''.
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@end quotation
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@end copying
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@c
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@c Title Page and Copyright
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@c
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@titlepage
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@title Enfuse
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@subtitle Fusing Multiple Images
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@subtitle with Enfuse version @value{VERSION}, @value{UPDATED}
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@author Andrew Mihal
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@page
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@vskip 0pt plus 1fill
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@insertcopying
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@end titlepage
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@ifnothtml
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@summarycontents
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@end ifnothtml
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@contents
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@c For the TeX output the List-of-Tables and List-of-Figures appear
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@c right after the Table-of-Contents. In all other formats they go
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@c right before the indices.
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@iftex
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@c Adjust page number so that we get roman numerals for the
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@c List-of-Tables and List-of-Figures. This screws up Texinfo's page
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@c count so that we must undo it later.
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@tex
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\global\pageno=-4
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@end tex
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@unnumbered List of Tables
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@listoffloats Table
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97
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@unnumbered List of Figures
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@listoffloats Figure
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@end iftex
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@c
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@c ``Top'' Node and Master Menu
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@c
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@ifnottex
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@node Top
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@top Enfuse
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This manual is for Enfuse (version@tie{}@value{VERSION},
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@value{UPDATED}), a program to merge different exposures of the same
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scene to produce an image that looks much like a tonemapped image.
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@end ifnottex
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@menu
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* Overview:: Overview of Enfuse's features
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* Workflow:: Enfuse's role in combining images
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* Invocation:: Command line options and arguments
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* Color Profiles:: How Enblend handles @acronym{ICC} color profiles
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* Weighting Functions:: Description of all weighting functions
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* Understanding Masks:: How to interpret masks and mask files
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* Tuning Memory Usage:: Balancing @acronym{RAM} and swap
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* Applications:: Possible applications of Enfuse
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* Helpful Programs:: Useful other programs
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* Bug Reports:: How to write bug reports
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* Authors:: Major contributors
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* FDL:: @acronym{GNU} Free Documentation License
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@ifnotdocbook
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* List of Tables:: List of all tables
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* List of Figures:: List of all figures
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* Program Index:: Names of programs referenced
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* Syntactic-Comment Index:: Keys of syntactic comments
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* Option Index:: Index of all options
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* General Index:: Topic index
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@end ifnotdocbook
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@detailmenu
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--- The Detailed Node Listing ---
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Overview
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Workflow
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* Standard Workflow:: The usual, all-in-one thing
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* External Mask Manipulation:: Fiddling around with the masks yourself
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149
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Invocation
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152
* Common Options:: General options
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* Extended Options:: Memory control and others
154
* Fusion Options:: Image fusion control
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* Expert Options:: Local contrast and local entropy selection configuration
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* Option Delimiters:: How to separate options' arguments
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158
Color Profiles
159
160
Weighting Functions
161
162
* Weighting Pixels:: General concept of weighting pixels
163
* Exposure Weighting:: Weighting by exposure
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* Saturation Weighting:: Weighting by saturation
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* Local Contrast Weighting:: Weighting by local contrast
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* Local Entropy Weighting:: Weighting by local entropy
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168
Weighting Algorithms
169
170
* Weighted Average:: Enfuse's default weighting algorithm
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* Disabling Averaging:: ``Super Trouper'' weighting for focus stacks
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Local Contrast Weighting
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* Standard Deviation:: Standard deviation (@acronym{SDev}) in a square of pixels
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* Laplacian of Gaussian:: @acronym{LoG}, a second derivative method
177
* Blend SDev and LoG:: Mix both methods
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* Scaling and Choice of Mode:: How parameters do not scale; neither does mode
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Understanding Masks
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182
Tuning Memory Usage
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Applications
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* What Images:: What makes images fusable?
187
* Repetition:: Just taking the same shot multiple times
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* Exposure Series:: Varying the exposure time
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* Flash Exposure Series:: Varying the flash output
190
* Polarization Series:: Changing the polarizer angle
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* Focus Stacks:: Stacking images with different in-focus distance
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Exposure Series
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* Exposure Series Tips:: Some hints for beginners
196
* Exposure Series Misconceptions:: What works despite the hype
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Focus Stacks
199
200
* Why Focus Stacks:: Why take the hassle?
201
* Preparing Focus Stacks:: How to get suitable input images
202
* Local Contrast Based Fusing:: Fundamental command line options
203
* Basic Focus Stacking:: Simple, standard deviation method
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* Advanced Focus Stacking:: Advanced, Laplacian technique
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* Expert Stacking:: Tips for focus stacking experts
206
207
Advanced Focus Stacking
208
209
* Local Contrast Problem:: What is the problem Kenneth?
210
* Laplacian Edge Detection:: Using a Laplacian-of-Gaussian to detect edges
211
* Local Contrast Enhancement:: Boosting local contrast before weighting
212
* Suppressing Noise or Recognizing Faint Edges:: The best of both worlds
213
* Focus Stacking Decision Tree:: What to do and how to fuse
214
215
Helpful Programs
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217
Bug Reports
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Authors
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FDL
222
@end detailmenu
223
@end menu
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@c
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@c Document Body
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@c
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@node Overview
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@chapter Overview
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233
@c Undo the roman page numbering we used for the Table-of-Contents,
234
@c the List-of-Tables, and the List-of-Figures.
235
@tex
236
\global\pageno=1
237
@end tex
238
239
@cindex overview
240
241
@cindex Mertens-Kautz-Van Reeth exposure fusion
242
Enfuse merges overlapping images using the
243
@sc{Mertens}-@sc{Kautz}-@sc{Van Reeth} exposure fusion
244
algorithm.@footnote{Tom Mertens, Jan Kautz, and Frank van Reeth,
245
``Exposure Fusion'', Proceedings of the 15th Pacific Conference on
246
Computer Graphics and Applications, pages 382--390.} This is a quick
247
way for example to blend differently exposed images into a nice output
248
image, without producing intermediate high-dynamic range
249
(@acronym{HDR}) images that are then tonemapped to a viewable image.
250
This simplified process often works much better than tonemapping
251
algorithms.
252
253
Enfuse can also be used to build extended depth-of-field
254
(@acronym{DOF}) images by blending a focus stack.
255
256
The idea is that pixels in the input images are weighted according to
257
qualities such as, for example, proper exposure, good local contrast,
258
or high saturation. These weights determine how much a given pixel
259
will contribute to the final image.
260
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@cindex Burt-Adelson multiresolution spline
262
A @sc{Burt}-@sc{Adelson} multiresolution spline blender@footnote{Peter
263
J. Burt and Edward H. Adelson, ``A Multiresolution Spline With
264
Application to Image Mosaics'', @acronym{ACM} Transactions on
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Graphics, @abbr{Vol@.} 2, @abbr{No@.} 4, October 1983, pages
266
217--236.} is used to combine the images according to the weights.
267
The multiresolution blending ensures that transitions between regions
268
where different images contribute are difficult to spot.
269
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Enfuse uses up to four criteria to judge the quality of a pixel, which
271
@ref{Table:weighting-criteria} briefly describes.
272
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@float Table,Table:weighting-criteria
274
@table @asis
275
@dbtitle{Weighting Criteria}
276
@item Exposure
277
@cindex weighting, exposure
278
The exposure criteria favors pixels with luminance close to the middle
279
of the range. These pixels are considered better exposed than those
280
with high or low luminance levels.
281
282
@item Saturation
283
@cindex weighting, saturation
284
The saturation criteria favors highly-saturated pixels. (Note that
285
saturation is only defined for color pixels.)
286
287
@item Local Contrast
288
@cindex weighting, local contrast
289
The contrast criteria favors pixels inside a high-contrast
290
neighborhood. Enfuse can use standard deviation, Laplacian magnitude,
291
or a blend of both as local contrast measure.
292
293
@item Local Entropy
294
@cindex weighting, local entropy
295
The entropy criteria prefers pixels inside a high-entropy
296
neighborhood. In addition, Enfuse allows the user to mitigate the
297
problem of noisy images when using entropy weighting by setting a
298
black threshold.
299
@end table
300
301
@caption{Enfuse's four weighting criteria. (Also see @ref{Table:default-weights} for the default weights of these criteria.)}
302
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@shortcaption{Weighting criteria}
304
@end float
305
306
For the concept of pixel weighting, and details on the different
307
weighting functions, see @ref{Weighting Functions}.
308
309
Adjust how much importance is given to each criterion by setting the
310
weight parameters on the command line. For example, if you set
311
@samp{--exposure-weight=1.0} and @samp{--saturation-weight=0.5},
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Enfuse will favor well-exposed pixels over highly-saturated pixels
313
when blending the source images. The effect of these parameters on
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the final result will not always be clear in advance. The quality of
315
the result is subject to your artistic interpretation. Playing with
316
the weights may or may not give a more pleasing result. The authors
317
encourage you to experiment, perhaps using
318
down-sized@footnote{Downsampling with a good interpolator reduces
319
noise, which might not desired to judge the image quality of the
320
original-size image. Cropping might be an alternative, though.} or
321
cropped images for speed.
322
323
@cindex alpha channel
324
@cindex channel, alpha
325
Enfuse expects but does not require each input image to have an alpha
326
channel. By setting the alpha values of pixels to zero, users can
327
manually remove those pixels from consideration when blending. If an
328
input image lacks an alpha channel, Enfuse will issue a warning and
329
continue assuming all pixels should contribute to the final output.
330
Any alpha value other than zero is interpreted as ``this pixel should
331
contribute to the final image''.
332
333
@cindex multi-layer image
334
@cindex image, multi-layer
335
@cindex multi-directory @acronym{TIFF}
336
@cindex @acronym{TIFF}, multi-directory
337
@cindex @command{tiffcopy}
338
@cindex @command{tiffsplit}
339
Enfuse reads all layers of multi-layer images, like, for example,
340
multi-directory @acronym{TIFF} images@footnote{Use utilities like,
341
e.g., @command{tiffcopy} and @command{tiffsplit} of LibTIFF to
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manipulate multi-directory @acronym{TIFF} images. @xref{Helpful
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Programs}.}. The input images are processed in the order they appear
344
on the command line. Multi-layer images are processed from the first
345
layer to the last before Enfuse considers the next image on the
346
command line.
347
348
@cindex SourceForge
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Find out more about Enfuse on its @uref{http://@/sourceforge.net/,
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SourceForge} @uref{http://@/enblend.sourceforge.net/, web page}.
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352
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@node Workflow
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@chapter Workflow
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@cindex workflow
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357
Enfuse is a part of a chain of tools to assemble images. It merges
358
photos of the same subject at the same location and same direction,
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but taken with varying exposure parameters.
360
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@menu
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* Standard Workflow:: The usual, all-in-one thing
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* External Mask Manipulation:: Fiddling around with the masks yourself
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@end menu
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366
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@node Standard Workflow
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@section Standard Workflow
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@cindex workflow, standard
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371
@include workflow.texi
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@node External Mask Manipulation
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@section External Mask Manipulation
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@cindex workflow, external mask manipulation
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@include external-masks.texi
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@node Invocation
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@chapter Invocation
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@cindex invocation
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@command{enfuse} [@var{OPTIONS}] [@code{--output=}@var{IMAGE}]
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@var{INPUT}@enddots{}
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@noindent
389
Fuse the sequence of images @var{INPUT}@dots{} into a single
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@var{IMAGE}.
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@cindex literal filename
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@cindex filename, literal
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@cindex response file
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Input images are either specified literally or via so-called response
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files (see below). The latter are an alternative to specifying image
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filenames on the command line.
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@menu
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* Image Requirements:: Input image requirements
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* Response Files:: Files listing the images' names
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* Common Options:: General options
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* Extended Options:: Memory control and others
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* Fusion Options:: Image fusion control
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* Expert Options:: Local contrast and local entropy selection configuration
407
* Option Delimiters:: How to separate options' arguments
408
@end menu
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410
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@node Image Requirements
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@section Image Requirements
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@cindex input image requirements
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415
All input images must comply with the following requirements.
416
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@itemize
418
@item
419
The images overlap.
420
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@item
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The images agree on their number of bits-per-channel, this is, their
423
``depth'':
424
@itemize --
425
@item
426
@code{UINT8},
427
@item
428
@code{UINT16},
429
@item
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@code{FLOAT},
431
@item
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etc.
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@end itemize
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See option@tie{}@option{--depth} below for an explanation of different
436
(output) depths.
437
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@item
439
Enfuse understands the images' filename extensions as well as their
440
file formats.
441
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You can check the supported extensions and formats by calling Enfuse
443
with the option pair @option{--version@tie{}--verbose} and scan the
444
output for @samp{Supported image formats} or @samp{Supported file
445
extensions}.
446
@end itemize
447
448
Moreover, there are some ``good practices'', which are not enforced by
449
the application, but almost certainly deliver superior results.
450
451
@itemize
452
@item
453
Either all files lack an @acronym{ICC} profile, or all images are
454
supplied with the @emph{same} @acronym{ICC} profile.
455
456
@item
457
If the images' meta-data contains resolution information
458
(``@acronym{DPI}''), it is the same for all pictures.
459
@end itemize
460
461
462
@node Response Files
463
@section Response Files
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@cindex response file
465
466
@include filespec.texi
467
468
469
@node Common Options
470
@section Common Options
471
@cindex options, common
472
473
Common options control some overall features of Enfuse.
474
475
Enfuse accepts arguments to any option in uppercase as well as in
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lowercase letters. For example, @samp{deflate}, @samp{Deflate} and
477
@samp{DEFLATE} as arguments to the @code{--compression} option
478
described below, all instruct Enfuse to use the @sc{Deflate}
479
compression scheme. This manual denotes all arguments in lowercase
480
for consistency.
481
482
@table @code
483
@item --compression=@var{COMPRESSION}
484
@opindex --compression
485
@cindex output file compression
486
@cindex compression
487
Write a compressed output file.
488
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Depending on the output file format, Enfuse accepts different values
490
for @var{COMPRESSION}.
491
492
@table @asis
493
@item @acronym{JPEG} format.
494
@cindex @acronym{JPEG} compression
495
@cindex compression, @acronym{JPEG}
496
497
The compression either is a literal integer or a keyword-option
498
combination.
499
500
@table @code
501
@item @var{LEVEL}
502
Set @acronym{JPEG} quality@tie{}@var{LEVEL}, where @var{LEVEL} is an
503
integer that ranges from 0--100.
504
505
@item jpeg[:@var{LEVEL}]
506
Same as above; without the optional argument just switch on (standard)
507
@acronym{JPEG} compression.
508
509
@item jpeg-arith[:@var{LEVEL}]
510
@cindex arithmetic @acronym{JPEG} compression
511
@cindex compression, arithmetic @acronym{JPEG}
512
Switch on arithmetic @acronym{JPEG} compression. With optional
513
argument set the arithmetic compression@tie{}@var{LEVEL}, where
514
@var{LEVEL} is an integer that ranges from 0--100.
515
@end table
516
517
@item @acronym{TIF} format.
518
Here, @var{COMPRESSION} is one of the keywords:
519
520
@table @code
521
@item none
522
Do not compress. This is the default.
523
524
@item deflate
525
@cindex deflate compression
526
@cindex compression, deflate
527
Use the @sc{Deflate} compression scheme also called
528
@acronym{ZIP}-in-@acronym{TIFF}. @sc{Deflate} is a lossless data
529
compression algorithm that uses a combination of the @acronym{LZ77}
530
algorithm and @sc{Huffman} coding.
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@item jpeg[:@var{LEVEL}]
533
@cindex compression, @acronym{JPEG}
534
Use @acronym{JPEG} compression. With optional argument set the
535
compression@tie{}@var{LEVEL}, where @var{LEVEL} is an integer that
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ranges from 0--100.
537
538
@item lzw
539
@cindex @acronym{LZW} compression
540
@cindex compression, @acronym{LZW}
541
Use @sc{Lempel}-@sc{Ziv}-@sc{Welch} (@acronym{LZW}) adaptive
542
compression scheme. @acronym{LZW} compression is lossless.
543
544
@item packbits
545
@cindex packbits compression
546
@cindex compression, packbits
547
Use @sc{PackBits} compression scheme. @sc{PackBits} is a particular
548
variant of run-length compression; it is lossless.
549
@end table
550
551
@item Any other format.
552
Other formats do not accept a @var{COMPRESSION} setting.
553
554
However, @uref{http://@/hci.iwr.uni-@/heidelberg.de/@/vigra/,
555
@acronym{VIGRA}} automatically compresses @file{png}-files with the
556
@sc{Deflate} method.
557
@end table
558
559
@item --layer-selector=@var{ALGORITHM}
560
@opindex --layer-selector
561
@cindex layer selection
562
@cindex layer selection
563
Override the standard layer selector algorithm, which is
564
@samp{@value{src::layer-selector}}.
565
566
This version of Enfuse offers the following algorithms:
567
@table @code
568
@item all-layers
569
@cindex layer selection, all-layers
570
Select all layers in all images.
571
572
@item first-layer
573
@cindex layer selection, first-layer
574
Select only first layer in each multi-layer image. For single-layer
575
images this is the same as @samp{all-layers}.
576
577
@item largest-layer
578
@cindex layer selection, largest-layer
579
Select largest layer in each multi-layer image, where the
580
``largeness'', this is the size is defined by the product of the layer
581
width and its height. The channel width of the layer is ignored. For
582
single-layer images this is the same as @samp{all-layers}.
583
584
@item no-layer
585
@cindex layer selection, no layer
586
Do not select any layer in any image.
587
588
This algorithm is useful to temporarily exclude some images in
589
response files.
590
@end table
591
592
@item -h
593
@itemx --help
594
@opindex -h
595
@opindex --help
596
Print information on the available options and exit.
597
598
@item -l @var{LEVELS}
599
@itemx --levels=@var{LEVELS}
600
@opindex -l
601
@opindex --levels
602
@cindex pyramid levels
603
@cindex levels, pyramid
604
Use at most this many @var{LEVELS} for pyramid @footnote{As
605
Dr.@tie{}Daniel Jackson correctly
606
@uref{http://stargate.wikia.com/@/wiki/@/The_@/Tomb, noted}, actually,
607
it is not a pyramid: ``Ziggaurat, it's a
608
@uref{http://en.wikipedia.org/@/wiki/@/Ziggaurat, Ziggaurat}.''}
609
blending if @var{LEVELS} is positive, or reduce the maximum number of
610
levels used by @minus{}@var{LEVELS} if @var{LEVELS} is negative;
611
@samp{auto} or @samp{automatic} restore the default, which is to use
612
the maximum possible number of levels for each overlapping region.
613
614
The number of levels used in a pyramid controls the balance between
615
local and global image features (contrast, saturation, @dots{}) in the
616
blended region. Fewer levels emphasize local features and suppress
617
global ones. The more levels a pyramid has, the more global features
618
will be taken into account.
619
620
As a guideline, remember that each new level works on a linear scale
621
twice as large as the previous one. So, the zeroth layer, the
622
original image, obviously defines the image at single-pixel scale, the
623
first level works at two-pixel scale, and generally, the @math{n}-th
624
level contains image data at @power{2, n}-pixel scale. This is the
625
reason why an image of
626
@math{width}@classictimes{}@/@math{height}@dmn{pixels} cannot be
627
deconstructed into a pyramid of more than
628
@ifinfo
629
@display
630
@math{floor(log_2(min(width, height)))}
631
@end display
632
@end ifinfo
633
@html
634
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
635
<mrowinline>
636
<mo>⌊</mo>
637
<mrowinline>
638
<msubinline>
639
<mo>log</mo>
640
<mn>2</mo>
641
</msubinline>
642
<mo>⁡</mo>
643
<mo>(</mo>
644
<mrowinline>
645
<mo>min</mo>
646
<mo>⁡</mo>
647
<mfencedinline>
648
<mi mathvariant="italic">width</mi>
649
<mi mathvariant="italic">height</mi>
650
</mfencedinline>
651
</mrowinline>
652
<mo>)</mo>
653
</mrowinline>
654
<mo>⌋</mo>
655
</mrowinline>
656
</mathinline>
657
@end html
658
@tex
659
$\lfloor \log_2(\min(\mathit{width}, \mathit{height})) \rfloor$
660
@end tex
661
@docbook
662
<inlineequation>
663
<mml:math>
664
<mml:apply>
665
<mml:floor/>
666
<mml:apply>
667
<mml:log/>
668
<mml:logbase>
669
<mml:cn>2</mml:cn>
670
</mml:logbase>
671
<mml:apply>
672
<mml:min/>
673
<mml:csymbol>
674
<mml:mi mathvariant="italic">width</mml:mi>
675
</mml:csymbol>
676
<mml:csymbol>
677
<mml:mi mathvariant="italic">height</mml:mi>
678
</mml:csymbol>
679
</mml:apply>
680
</mml:apply>
681
</mml:apply>
682
</mml:math>
683
</inlineequation>
684
@end docbook
685
levels.
686
687
If too few levels are used, ``halos'' around regions of strong local
688
feature variation can show up. On the other hand, if too many levels
689
are used, the image might contain too much global features. Usually,
690
the latter is not a problem, but is highly desired. This is the
691
reason, why the default is to use as many levels as is possible given
692
the size of the overlap regions. Enfuse may still use a smaller
693
number of levels if the geometry of the overlap region demands.
694
695
Positive values of @var{LEVELS} limit the maximum number of pyramid
696
levels. Depending on the size and geometry of the overlap regions
697
this may or may not influence any pyramid. Negative values of
698
@var{LEVELS} reduce the number of pyramid levels below the maximum no
699
matter what the actual maximum is and thus always influence all
700
pyramids. Use @samp{auto} or @samp{automatic} as @var{LEVELS} to
701
restore the automatic calculation of the maximum number of levels.
702
703
The valid range of the absolute value of @var{LEVELS} is
704
@value{src::minimum-pyramid-levels} to
705
@value{src::maximum-pyramid-levels}.
706
707
@item -o
708
@itemx --output=@var{FILE}
709
@opindex -o
710
@opindex --output
711
Place output in @var{FILE}.
712
713
@cindex @file{@value{src::default-output-filename}}
714
@cindex default output filename
715
@cindex output filename, default
716
If @option{--output} is not specified, the default is to put the
717
resulting image in @file{@value{src::default-output-filename}}.
718
719
@item --parameter=@var{KEY}[=@var{VALUE}]:@dots{}
720
Set a @var{KEY}-@var{VALUE} pair, where @var{VALUE} is optional. This
721
option is cumulative. Separate multiple pairs with the usual numeric
722
delimiters.
723
724
This option has the negated form @option{--no-parameter},
725
@opindex --no-parameter
726
which takes one or more @var{KEY}s and removes them from the list of
727
defined parameters. The special key@tie{}@samp{*} deletes all
728
parameters at once.
729
730
Parameters allow the developers to change the internal
731
workings of Enfuse without the need to recompile.
732
733
@item -v
734
@itemx --verbose[=@var{LEVEL}]
735
@opindex -v
736
@opindex --verbose
737
Without an argument, increase the verbosity of progress reporting.
738
Giving more @option{--verbose}@tie{}options will make Enfuse more
739
verbose. Directly set a verbosity level with a non-negative integral
740
@var{LEVEL}.
741
742
Each level includes all messages of the lower levels.
743
744
@table @asis
745
@item Level
746
Messages
747
748
@item 0
749
only warnings and errors
750
751
@item 1
752
reading and writing of images
753
754
@item 2
755
mask generation, pyramid, and blending
756
757
@item 3
758
reading of response files, color conversions
759
760
@item 4
761
image sizes, bounding boxes and intersection sizes
762
763
@item 5
764
detailed information on the optimizer runs (Enblend only)
765
766
@item 6
767
estimations of required memory in selected processing steps
768
@end table
769
770
The default verbosity level of Enfuse is
771
@value{src::default-verbosity-level}.
772
773
@item -V
774
@itemx --version
775
@opindex -V
776
@opindex --version
777
Output information on the Enfuse version.
778
779
Team this option with @option{--verbose} to show configuration
780
details, like the extra features that have been compiled in.
781
782
@item -w
783
@itemx --wrap=@var{MODE}
784
@opindex -w
785
@opindex --wrap
786
@cindex 360@textdegree{} panoramas
787
@cindex wrap around
788
Blend around the boundaries of the panorama.
789
790
As this option significantly increases memory usage and computation
791
time only use it, if the panorama will be
792
793
@itemize
794
@item
795
consulted for any kind measurement, this is, all boundaries must match
796
as accurately as possible, or
797
798
@item
799
printed out and the boundaries glued together, or
800
801
@item
802
@cindex virtual reality
803
fed into a virtual reality (@abbr{VR}) generator, which creates a
804
seamless environment.
805
@end itemize
806
807
Otherwise, always avoid this option!
808
809
With this option, Enfuse treats the panorama of width@tie{}@math{w}
810
and height@tie{}@math{h} as an infinite data structure, where each
811
pixel@tie{}@math{P(x, y)} of the input images represents the set of
812
pixels
813
@ifinfo
814
@math{S_P(x, y)}
815
@end ifinfo
816
@html
817
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
818
<mrowinline>
819
<msubinline>
820
<mi>S</mi>
821
<mi>P</mi>
822
</msubinline>
823
<mfencedinline>
824
<mi>x</mi>
825
<mi>y</mi>
826
</mfencedinline>
827
</mrowinline>
828
</mathinline>
829
@end html
830
@tex
831
$S_P(x, y)$
832
@end tex
833
@docbook
834
<inlineequation>
835
<mml:math>
836
<mml:apply>
837
<mml:csymbol>
838
<mml:msub>
839
<mml:mi>S</mml:mi>
840
<mml:mi>P</mml:mi>
841
</mml:msub>
842
</mml:csymbol>
843
<mml:ci>x</mml:ci>
844
<mml:ci>y</mml:ci>
845
</mml:apply>
846
</mml:math>
847
</inlineequation>
848
@end docbook
849
@footnote{Solid-state physicists will be reminded of the
850
@uref{http://@/en.wikipedia.org/@/wiki/@/Born-@/von_@/Karman_@/boundary_@/condition,
851
@sc{Born}-@sc{von@tie{}K@'arm@'an} boundary condition}.}.
852
853
@var{MODE} takes the following values:
854
855
@table @samp
856
@item none
857
@itemx open
858
This is a ``no-op''; it has the same effect as not giving
859
@option{--wrap} at all. The set of input images is considered open at
860
its boundaries.
861
862
@item horizontal
863
Wrap around horizontally:
864
@ifinfo
865
@display
866
@math{S_P(x, y) = @{P(x + m * w, y): m in Z@}.}
867
@end display
868
@end ifinfo
869
@html
870
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
871
<mrow>
872
<msub>
873
<mi>S</mi>
874
<mi>P</mi>
875
</msub>
876
<mfenced>
877
<mi>x</mi>
878
<mi>y</mi>
879
</mfenced>
880
<mo>=</mo>
881
<mrow>
882
<mo>{</mo>
883
<mrow>
884
<mi>P</mi>
885
<mfenced>
886
<mrow>
887
<mi>x</mi>
888
<mo>+</mo>
889
<mi>m</mi>
890
<mo>⁢</mo>
891
<mi>w</mi>
892
</mrow>
893
<mi>y</mi>
894
</mfenced>
895
</mrow>
896
<mo>:</mo>
897
<mrow>
898
<mi>m</mi>
899
<mtext>  in  </mtext>
900
<mi>Z</mi>
901
</mrow>
902
<mo>}</mo>
903
</mrow>
904
<mtext>.</mtext>
905
</mrow>
906
</math>
907
@end html
908
@tex
909
$$
910
S_P(x, y) = \{P(x + m w, y): m \in Z\}.
911
$$
912
@end tex
913
@docbook
914
<informalequation>
915
<mml:math>
916
<mml:reln>
917
<mml:eq/>
918
<mml:apply>
919
<mml:csymbol>
920
<mml:msub>
921
<mml:mi>S</mml:mi>
922
<mml:mi>P</mml:mi>
923
</mml:msub>
924
</mml:csymbol>
925
<mml:ci>x</mml:ci>
926
<mml:ci>y</mml:ci>
927
</mml:apply>
928
<mml:set>
929
<mml:bvar>
930
<mml:apply>
931
<mml:ci>P</mml:ci>
932
<mml:apply>
933
<mml:plus/>
934
<mml:ci>x</mml:ci>
935
<mml:apply>
936
<mml:times/>
937
<mml:ci>m</mml:ci>
938
<mml:ci>w</mml:ci>
939
</mml:apply>
940
</mml:apply>
941
<mml:ci>y</mml:ci>
942
</mml:apply>
943
</mml:bvar>
944
<mml:condition>
945
<mml:apply>
946
<mml:in/>
947
<mml:ci>m</mml:ci>
948
<mml:ci>Z</mml:ci>
949
</mml:apply>
950
</mml:condition>
951
</mml:set>
952
</mml:reln>
953
</mml:math>
954
</informalequation>
955
@end docbook
956
957
This is useful for 360@textdegree{} horizontal panoramas as it
958
eliminates the left and right borders.
959
960
@item vertical
961
Wrap around vertically:
962
@ifinfo
963
@display
964
@math{S_P(x, y) = @{P(x, y + n * h): m in Z@}.}
965
@end display
966
@end ifinfo
967
@html
968
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
969
<mrow>
970
<msub>
971
<mi>S</mi>
972
<mi>P</mi>
973
</msub>
974
<mfenced>
975
<mi>x</mi>
976
<mi>y</mi>
977
</mfenced>
978
<mo>=</mo>
979
<mrow>
980
<mo>{</mo>
981
<mrow>
982
<mi>P</mi>
983
<mfenced>
984
<mi>x</mi>
985
<mrow>
986
<mi>y</mi>
987
<mo>+</mo>
988
<mi>n</mi>
989
<mo>⁢</mo>
990
<mi>h</mi>
991
</mrow>
992
</mfenced>
993
</mrow>
994
<mo>:</mo>
995
<mrow>
996
<mi>n</mi>
997
<mtext>  in  </mtext>
998
<mi>Z</mi>
999
</mrow>
1000
<mo>}</mo>
1001
</mrow>
1002
<mtext>.</mtext>
1003
</mrow>
1004
</math>
1005
@end html
1006
@tex
1007
$$
1008
S_P(x, y) = \{P(x, y + n h): n \in Z\}.
1009
$$
1010
@end tex
1011
1012
This is useful for 360@textdegree{} vertical panoramas, as it
1013
eliminates the top and bottom borders.
1014
1015
@item both
1016
@itemx horizontal+vertical
1017
@itemx vertical+horizontal
1018
Wrap around both horizontally and vertically:
1019
@ifinfo
1020
@display
1021
@math{S_P(x, y) = @{P(x + m * w, y + n * h): m, n in Z@}.}
1022
@end display
1023
@end ifinfo
1024
@html
1025
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
1026
<mrow>
1027
<msub>
1028
<mi>S</mi>
1029
<mi>P</mi>
1030
</msub>
1031
<mfenced>
1032
<mi>x</mi>
1033
<mi>y</mi>
1034
</mfenced>
1035
<mo>=</mo>
1036
<mrow>
1037
<mo>{</mo>
1038
<mrow>
1039
<mi>P</mi>
1040
<mfenced>
1041
<mrow>
1042
<mi>x</mi>
1043
<mo>+</mo>
1044
<mi>m</mi>
1045
<mo>⁢</mo>
1046
<mi>w</mi>
1047
</mrow>
1048
<mrow>
1049
<mi>y</mi>
1050
<mo>+</mo>
1051
<mi>n</mi>
1052
<mo>⁢</mo>
1053
<mi>h</mi>
1054
</mrow>
1055
</mfenced>
1056
</mrow>
1057
<mo>:</mo>
1058
<mrow>
1059
<mrow>
1060
<mi>m</mi>
1061
<mo>,</mo>
1062
<mi>n</mi>
1063
</mrow>
1064
<mtext>  in  </mtext>
1065
<mi>Z</mi>
1066
</mrow>
1067
<mo>}</mo>
1068
</mrow>
1069
<mtext>.</mtext>
1070
</mrow>
1071
</math>
1072
@end html
1073
@tex
1074
$$
1075
S_P(x, y) = \{P(x + m w, y + n h): m, n \in Z\}.
1076
$$
1077
@end tex
1078
@docbook
1079
<informalequation>
1080
<mml:math>
1081
<mml:reln>
1082
<mml:eq/>
1083
<mml:apply>
1084
<mml:csymbol>
1085
<mml:msub>
1086
<mml:mi>S</mml:mi>
1087
<mml:mi>P</mml:mi>
1088
</mml:msub>
1089
</mml:csymbol>
1090
<mml:ci>x</mml:ci>
1091
<mml:ci>y</mml:ci>
1092
</mml:apply>
1093
<mml:set>
1094
<mml:bvar>
1095
<mml:apply>
1096
<mml:ci>P</mml:ci>
1097
<mml:apply>
1098
<mml:plus/>
1099
<mml:ci>x</mml:ci>
1100
<mml:apply>
1101
<mml:times/>
1102
<mml:ci>m</mml:ci>
1103
<mml:ci>w</mml:ci>
1104
</mml:apply>
1105
</mml:apply>
1106
<mml:apply>
1107
<mml:plus/>
1108
<mml:ci>y</mml:ci>
1109
<mml:apply>
1110
<mml:times/>
1111
<mml:ci>n</mml:ci>
1112
<mml:ci>h</mml:ci>
1113
</mml:apply>
1114
</mml:apply>
1115
</mml:apply>
1116
</mml:bvar>
1117
<mml:condition>
1118
<mml:apply>
1119
<mml:and/>
1120
<mml:apply>
1121
<mml:in/>
1122
<mml:ci>n</mml:ci>
1123
<mml:ci>Z</mml:ci>
1124
</mml:apply>
1125
<mml:apply>
1126
<mml:in/>
1127
<mml:ci>m</mml:ci>
1128
<mml:ci>Z</mml:ci>
1129
</mml:apply>
1130
</mml:apply>
1131
</mml:condition>
1132
</mml:set>
1133
</mml:reln>
1134
</mml:math>
1135
</informalequation>
1136
@end docbook
1137
1138
In this mode, both left and right borders, as well as top and bottom
1139
borders, are eliminated.
1140
@end table
1141
1142
Specifying @option{--wrap} without @var{MODE} selects horizontal
1143
wrapping.
1144
@end table
1145
1146
1147
@node Extended Options
1148
@section Extended Options
1149
@cindex options, extended
1150
1151
Extended options control the image cache, the color model, and the
1152
cropping of the output image.
1153
1154
@table @code
1155
@item -b @var{BLOCKSIZE}
1156
@opindex -b
1157
@cindex image cache, block size
1158
Set the @var{BLOCKSIZE} in kilobytes (@acronym{KB}) of Enfuse's image
1159
cache.
1160
1161
This is the amount of data that Enfuse will move to and from the disk
1162
at one time. The default is @value{default-image-cache-blocksize},
1163
which should be ok for most systems. See @ref{Tuning Memory Usage}
1164
for details.
1165
1166
Note that Enfuse must have been compiled with the image-cache feature
1167
for this option to be effective. Find out about extra features with
1168
@code{enfuse --version --verbose}.
1169
1170
@item -c
1171
@itemx --ciecam
1172
@opindex -c
1173
@opindex --ciecam
1174
@cindex color appearance model
1175
@cindex @acronym{CIECAM02}
1176
Force the use of the @acronym{CIECAM02} color appearance model for
1177
blending colors instead of blending inside the @acronym{RGB} color
1178
cube.
1179
1180
@cindex color profile
1181
@cindex @acronym{ICC} profile
1182
@cindex profile, @acronym{ICC}
1183
@cindex @acronym{sRGB} color space
1184
@cindex color space, @acronym{sRGB}
1185
All input files should have identical @acronym{ICC} profiles when this
1186
option is specified. If no @acronym{ICC} profile is present, Enfuse
1187
assumes that all images use the @acronym{sRGB} color space.
1188
@xref{Color Profiles}.
1189
1190
Please keep in mind that using @acronym{CIECAM02} blending may change
1191
the colors in the output image.
1192
1193
This option can be negated; see option@tie{}@option{--no-ciecam}
1194
below.
1195
1196
@item -d
1197
@itemx --depth=@var{DEPTH}
1198
@opindex -d
1199
@opindex --depth
1200
@cindex bits per channel
1201
@cindex channel width
1202
Force the number of bits per channel and the numeric format of the
1203
output image.
1204
1205
Enfuse always uses a smart way to change the channel depth, to assure
1206
highest image quality (at the expense of memory), whether
1207
requantization is implicit because of the output format or explicit
1208
with option@tie{}@option{--depth}.
1209
1210
@itemize
1211
@item
1212
If the output-channel width is larger than the input-channel width of
1213
the input images, the input images' channels are widened to the output
1214
channel width immediately after loading, that is, as soon as possible.
1215
Enfuse then performs all blending operations at the output-channel
1216
width, thereby preserving minute color details which can appear in the
1217
blending areas.
1218
1219
@item
1220
If the output-channel width is smaller than the input-channel width of
1221
the input images, the output image's channels are narrowed only right
1222
before it is written to disk, that is, as late as possible. Thus the
1223
data benefits from the wider input channels for the longest time.
1224
@end itemize
1225
1226
All @var{DEPTH} specifications are valid in lowercase as well as
1227
uppercase letters. For integer format, use
1228
1229
@table @asis
1230
@item @code{8}, @code{uint8}
1231
Unsigned 8@dmn{bit}; range: 0..255
1232
@item @code{int16}
1233
Signed 16@dmn{bit}; range: @minus{}32768..32767
1234
@item @code{16}, @code{uint16}
1235
Unsigned 16@dmn{bit}; range: 0..65535
1236
@item @code{int32}
1237
Signed 32@dmn{bit}; range: @minus{}2147483648..2147483647
1238
@item @code{32}, @code{uint32}
1239
Unsigned 32@dmn{bit}; range: 0..4294967295
1240
@end table
1241
1242
For floating-point format, use
1243
1244
@c Minimum positive normalized value: 2^(2 - 2^k)
1245
@c Epsilon: 2^(1 - n)
1246
@c Maximum finite value: (1 - 2^(-n)) * 2^(2^k)
1247
1248
@table @asis
1249
@c IEEE single: 32 bits, n = 24, k = 32 - n - 1 = 7
1250
@item @code{r32}, @code{real32}, @code{float}
1251
@cindex @acronym{IEEE754} single precision float
1252
@cindex single precision float, @acronym{IEEE754}
1253
@acronym{IEEE754} single precision floating-point, 32@dmn{bit} wide,
1254
24@dmn{bit} significant
1255
1256
@itemize
1257
@item
1258
Minimum normalized value: @semilog{1.2, -38}
1259
@item
1260
Epsilon: @semilog{1.2, -7}
1261
@item
1262
Maximum finite value: @semilog{3.4, 38}
1263
@end itemize
1264
1265
@c IEEE double: 64 bits, n = 53, k = 64 - n - 1 = 10
1266
@item @code{r64}, @code{real64}, @code{double}
1267
@cindex @acronym{IEEE754} double precision float
1268
@cindex double precision float, @acronym{IEEE754}
1269
@acronym{IEEE754} double precision floating-point, 64@dmn{bit} wide,
1270
53@dmn{bit} significant
1271
1272
@itemize
1273
@item
1274
Minimum normalized value: @semilog{2.2, -308}
1275
@item
1276
Epsilon: @semilog{2.2, -16}
1277
@item
1278
Maximum finite value: @semilog{1.8, 308}
1279
@end itemize
1280
@end table
1281
1282
If the requested @var{DEPTH} is not supported by the output file
1283
format, Enfuse warns and chooses the @var{DEPTH} that matches best.
1284
1285
@cindex @acronym{OpenEXR}, data format
1286
The @acronym{OpenEXR} data format is treated as
1287
@acronym{IEEE754}@tie{}float internally. Externally, on disk,
1288
@acronym{OpenEXR} data is represented by ``half'' precision
1289
floating-point numbers.
1290
1291
@c ILM half: 16 bits, n = 10, k = 16 - n - 1 = 5
1292
@cindex @acronym{OpenEXR}, half precision float
1293
@cindex half precision float, @acronym{OpenEXR}
1294
@uref{http://@/www.openexr.com/@/about.html#@/features,
1295
@acronym{OpenEXR}} half precision floating-point, 16@dmn{bit} wide,
1296
10@dmn{bit} significant
1297
1298
@itemize
1299
@item
1300
Minimum normalized value: @semilog{9.3, -10}
1301
@item
1302
Epsilon: @semilog{2.0, -3}
1303
@item
1304
Maximum finite value: @semilog{4.3, 9}
1305
@end itemize
1306
1307
@item -f @var{WIDTH}x@var{HEIGHT}
1308
@itemx -f @var{WIDTH}x@var{HEIGHT}+x@var{XOFFSET}+y@var{YOFFSET}
1309
@opindex -f
1310
@cindex output image, set size of
1311
@cindex canvas size
1312
@cindex size, canvas
1313
Ensure that the minimum ``canvas'' size of the output image is at
1314
least @var{WIDTH}@classictimes{}@/@var{HEIGHT}. Optionally specify
1315
the @var{XOFFSET} and @var{YOFFSET}, too.
1316
1317
@pindex nona @r{(Hugin)}
1318
@pindex hugin
1319
This option only is useful when the input images are cropped
1320
@acronym{TIFF} files, such as those produced by
1321
@command{nona}@footnote{The stitcher @command{nona} is part of Hugin.
1322
@xref{Helpful Programs}.}.
1323
1324
Note that option@tie{}@option{-f} neither rescales the output image,
1325
nor shrinks the canvas size below the minimum size occupied by the
1326
union of all input images.
1327
1328
@item --fallback-profile=@var{PROFILE-FILENAME}
1329
@opindex --fallback-profile
1330
@cindex profile, fallback
1331
@cindex fallback profile
1332
@cindex @acronym{CIECAM02}
1333
Use the @acronym{ICC} profile in @var{PROFILE-FILENAME} instead of the
1334
default @acronym{sRGB}. See option@tie{}@option{--ciecam} and
1335
@ref{Color Profiles}.
1336
1337
This option only is effective if the input images come without color
1338
profiles and blending is performed in @acronym{CIECAM02} color
1339
appearance model.
1340
1341
@item -g
1342
@opindex -g
1343
@cindex alpha channel, associated
1344
Save alpha channel as ``associated''. See the
1345
@uref{http://@/www.awaresystems.be/@/imaging/@/tiff/@/tifftags/@/extrasamples.html,
1346
@acronym{TIFF} documentation} for an explanation.
1347
1348
@pindex gimp
1349
@pindex cinepaint
1350
Gimp (before version@tie{}2.0) and CinePaint (@pxref{Helpful
1351
Programs}) exhibit unusual behavior when loading images with
1352
unassociated alpha channels. Use option @option{-g} to work around
1353
this problem. With this flag Enfuse will create the output image
1354
with the associated alpha tag set, even though the image is really
1355
unassociated alpha.
1356
1357
@item -m @var{CACHESIZE}
1358
@opindex -m
1359
@cindex image cache, cache size
1360
Set the @var{CACHESIZE} in megabytes (@acronym{MB}) of Enfuse's image
1361
cache.
1362
1363
This is the amount of memory Enfuse will use for storing image data
1364
before swapping to disk. The default is
1365
@value{default-image-cache-cachesize}, which is good for systems with
1366
3--4@dmn{gigabytes} (@acronym{GB}) of @acronym{RAM}. See @ref{Tuning
1367
Memory Usage} for details.
1368
1369
Note that Enfuse must have been compiled with the image-cache feature
1370
for this option to be effective. Find out about extra features with
1371
@code{enfuse --version --verbose}.
1372
1373
@item --no-ciecam
1374
@opindex --no-ciecam
1375
@cindex color appearance model
1376
@cindex @acronym{CIECAM02}
1377
Disable the use of the @acronym{CIECAM02} color appearance model for
1378
blending colors.
1379
1380
See option@tie{}@option{--ciecam} for details. Also see @ref{Color
1381
Profiles}.
1382
@end table
1383
1384
1385
@node Fusion Options
1386
@section Fusion Options
1387
@cindex options, fusion
1388
1389
Fusion options define the proportion to which each input image's pixel
1390
contributes to the output image.
1391
1392
@table @code
1393
@item --contrast-weight=@var{WEIGHT}
1394
@opindex --contrast-weight
1395
@cindex weight, local contrast
1396
1397
Sets the relative @var{WEIGHT} of high local-contrast pixels.
1398
1399
Valid range: @value{src::minimum-weight-contrast} @leq{} @var{WEIGHT}
1400
@leq{} @value{src::maximum-weight-contrast}.
1401
1402
Default: @value{src::default-weight-contrast}.
1403
1404
See @ref{Local Contrast Weighting} and @ref{Expert Options, Option
1405
contrast-window-size}.
1406
1407
@item --entropy-weight=@var{WEIGHT}
1408
@opindex --entropy-weight
1409
@cindex weight, entropy
1410
1411
Sets the relative @var{WEIGHT} of high local entropy pixels.
1412
1413
Valid range: @value{src::minimum-weight-entropy} @leq{} @var{WEIGHT}
1414
@leq{} @value{src::maximum-weight-entropy}.
1415
1416
Default: @value{src::default-weight-entropy}.
1417
1418
See @ref{Local Entropy Weighting} and @ref{Expert Options, Options
1419
entropy-window-size and entropy-cutoff}.
1420
1421
@item --exposure-weight=@var{WEIGHT}
1422
@opindex --exposure-weight
1423
@cindex weight, exposure
1424
1425
Sets the relative @var{WEIGHT} of the well-exposedness criterion.
1426
Increasing this weight relative to the others will make well-exposed
1427
pixels contribute more to the final output.
1428
1429
Valid range: @value{src::minimum-weight-exposure} @leq{} @var{WEIGHT}
1430
@leq{} @value{src::maximum-weight-exposure}.
1431
1432
Default: @value{src::default-weight-exposure}.
1433
1434
@xref{Exposure Weighting}.
1435
1436
@item --exposure-mu=@var{MEAN}
1437
@opindex --exposure-mu
1438
1439
Set the @var{MEAN} (this is, the center) of the Gaussian exposure
1440
weight curve.
1441
1442
Valid range: @value{src::minimum-exposure-mu} @leq{} @var{MEAN}
1443
@leq{} @value{src::maximum-exposure-mu}.
1444
1445
Default: @value{src::default-exposure-mu}.
1446
1447
Use this option to fine-tune exposure weighting (@pxref{Exposure
1448
Weighting}).
1449
1450
@item --exposure-sigma=@var{STD-DEV}
1451
@opindex --exposure-sigma
1452
1453
Standard deviation @var{STD-DEV} of the Gaussian exposure weight
1454
curve. Low numbers give less weight to pixels that are far from
1455
@option{--wMu} and vice versa.
1456
1457
Valid range: @var{STD-DEV} @geq{} @value{src::minimum-exposure-sigma}.
1458
1459
Default: @value{src::default-exposure-sigma}.
1460
1461
Use this option to fine-tune exposure weighting (@pxref{Exposure
1462
Weighting}).
1463
1464
@item --saturation-weight=@var{WEIGHT}
1465
@opindex --saturation-weight
1466
1467
Sets the relative @var{WEIGHT} of high-saturation pixels. Increasing
1468
this weight makes pixels with high saturation contribute more to the
1469
final output.
1470
1471
Valid range: @value{src::minimum-weight-saturation}
1472
@leq{} @var{WEIGHT} @leq{} @value{src::maximum-weight-saturation}.
1473
1474
Default: @value{src::default-weight-saturation}.
1475
1476
Saturation weighting is only defined for color images.
1477
@xref{Saturation Weighting}.
1478
@end table
1479
1480
1481
@node Expert Options
1482
@section Expert Options
1483
@cindex options, expert
1484
1485
Expert options influence the workings of Enfuse that require the user
1486
to read the manual before applying them successfully.
1487
1488
@table @code
1489
@item --contrast-edge-scale=@var{EDGE-SCALE}
1490
@itemx --contrast-edge-scale=@var{EDGE-SCALE}:@var{LCE-SCALE}:@var{LCE-FACTOR}
1491
@opindex --contrast-edge-scale
1492
1493
@cindex Laplacian-of-Gaussian
1494
A non-zero value for @var{EDGE-SCALE} switches on the
1495
Laplacian-of-Gaussian (@acronym{LoG}) edge detection algorithm.
1496
@var{EDGE-SCALE} is the radius of the Gaussian used in the search for
1497
edges. Default: @value{src::default-edge-scale}@dmn{pixels}.
1498
1499
A positive @var{LCE-SCALE} turns on local contrast enhancement
1500
(@acronym{LCE}) before the @acronym{LoG} edge detection.
1501
@var{LCE-SCALE} is the radius of the Gaussian used in the enhancement
1502
step, @var{LCE-FACTOR} is the weight factor (``strength'').
1503
1504
@var{enhanced} = (1 + @var{LCE-FACTOR}) @classictimes{} @var{original}
1505
@minus{} @var{LCE-FACTOR} @classictimes{} Gaussian@/Smooth(@var{original},
1506
@var{LCE-SCALE}).
1507
1508
@var{LCE-SCALE} defaults to @value{src::default-lce-scale} pixels and
1509
@var{LCE-FACTOR} defaults to @value{src::default-lce-factor}. Append
1510
@samp{%} to @var{LCE-SCALE} to specify the radius as a percentage of
1511
@var{EDGE-SCALE}. Append @samp{%} to @var{LCE-FACTOR} to specify the
1512
weight as a percentage.
1513
1514
@item --contrast-min-curvature=@var{CURVATURE}
1515
@opindex --contrast-min-curvature
1516
1517
Define the minimum @var{CURVATURE} for the @acronym{LoG} edge
1518
detection. Default: @value{src::default-minimum-curvature}. Append a
1519
@samp{%} to specify the minimum curvature relative to maximum pixel
1520
value in the source image (for example 255 or 65535).
1521
1522
A positive value makes Enfuse use the local contrast data (controlled
1523
with @option{--contrast-window-size}) for curvatures less than
1524
@var{CURVATURE} and @acronym{LoG} data for values above it.
1525
1526
A negative value truncates all curvatures less than
1527
@minus{}@var{CURVATURE} to zero. Values above @var{CURVATURE} are
1528
left unchanged. This effectively suppresses weak edges.
1529
1530
@item --contrast-window-size=@var{SIZE}
1531
@opindex --contrast-window-size
1532
1533
Set the window @var{SIZE} for local contrast analysis. The window
1534
will be a square of @var{SIZE}@classictimes{}@/@var{SIZE} pixels. If
1535
given an even @var{SIZE}, Enfuse will automatically use the next odd
1536
number.
1537
1538
For contrast analysis @var{SIZE} values larger than 5 might result in
1539
a blurry composite image. Values of 3 and 5 have given good results
1540
on focus stacks.
1541
1542
Valid range: @var{SIZE} @geq{} @value{src::minimum-contrast-window-size}.
1543
1544
Default: @value{src::default-contrast-window-size}@dmn{pixels}.
1545
1546
See also @ref{Fusion Options, Option --contrast-weight} and
1547
@option{--hard-mask} below.
1548
1549
@item --entropy-cutoff=@var{LOWER-CUTOFF}
1550
@itemx --entropy-cutoff=@var{LOWER-CUTOFF}:@var{UPPER-CUTOFF}
1551
@opindex --entropy-cutoff
1552
1553
The first form defines the lower cutoff value below which pixels are
1554
treated as pure black when calculating the local entropy. The second
1555
form also defines the upper cutoff value above which pixels are
1556
treated as pure white.
1557
1558
For color images @var{LOWER-CUTOFF} and @var{UPPER-CUTOFF} are applied
1559
separately and independently to each channel.
1560
1561
Defaults: @value{src::default-entropy-lower-cutoff} for
1562
@var{LOWER-CUTOFF} and @value{src::default-entropy-upper-cutoff} for
1563
@var{UPPER-CUTOFF}, that is, all pixels' values are taken into
1564
account. Append a @samp{%} to specify the cutoff relative to maximum
1565
pixel value in the source image (for example 255 or 65535).
1566
@ref{Figure:entropy-cutoff} shows an example.
1567
1568
@float Figure,Figure:entropy-cutoff
1569
@vimage{entropy-cutoff}
1570
1571
@caption{Linear lightness@tie{}@var{Y} in comparison with an entropy-cutoff function for @var{LOWER-CUTOFF} = 5% and @var{UPPER-CUTOFF} = 90%, which are rather extreme values. Please note that we have shifted the original lightness curve up and the cut-off curve down by a very small @var{Offset} to emphasize that the proportional part of @var{Y} remains unaltered under the cut-off operation.}
1572
1573
@shortcaption{Entropy cutoff function}
1574
@end float
1575
1576
Note that a high @var{LOWER-CUTOFF} value lightens the resulting
1577
image, as dark (and presumably noisy) pixels are averaged with
1578
@emph{equal} weights. With @samp{--entropy-cutoff=0}, the default, on
1579
the other hand, ``noise'' might be interpreted as high entropy and the
1580
noisy pixels get a high weight, which in turn renders the resulting
1581
image darker. Analogously, a low @var{UPPER-CUTOFF} darkens the
1582
output image.
1583
1584
@item --entropy-window-size=@var{SIZE}
1585
@opindex --entropy-window-size
1586
1587
Window @var{SIZE} for local entropy analysis. The window will be a
1588
square of @var{SIZE}@classictimes{}@/@var{SIZE} pixels.
1589
1590
In the entropy calculation @var{SIZE} values of 3 to 7 yield an
1591
acceptable compromise of the locality of the information and the
1592
significance of the local entropy value itself.
1593
1594
Valid range: @var{SIZE} @geq{} @value{src::minimum-entropy-window-size}.
1595
1596
Default: @value{src::default-entropy-window-size}@dmn{pixels}.
1597
1598
If given an even @var{SIZE} Enfuse will automatically use the next odd
1599
number.
1600
1601
@item --exposure-cutoff=@var{LOWER-CUTOFF}
1602
@itemx --exposure-cutoff=@var{LOWER-CUTOFF}:@var{UPPER-CUTOFF}
1603
@itemx --exposure-cutoff=@var{LOWER-CUTOFF}:@var{UPPER-CUTOFF}:@var{LOWER-PROJECTOR}:@var{UPPER-PROJECTOR}
1604
@opindex --exposure-cutoff
1605
1606
The first form sets the weight for all pixels below the lower cutoff
1607
to zero. The second form sets the lower cutoff and the upper cutoff
1608
at the same time. For color images the values of @var{LOWER-CUTOFF}
1609
and @var{UPPER-CUTOFF} refer to the gray-scale projection as selected
1610
with the option @option{--gray-projector}.
1611
1612
The impact of this option is similar, but not identical to
1613
transforming @emph{all} input images with
1614
@uref{http://@/www.imagemagick.org/, ImageMagick's} @command{convert}
1615
(@pxref{Helpful Programs}) prior to fusing with the following
1616
commands.
1617
1618
@example
1619
@group
1620
# First form
1621
convert IMAGE \
1622
\( +clone -threshold LOWER-CUTOFF \) \
1623
-compose copy_opacity -composite \
1624
MASKED-IMAGE
1625
@end group
1626
1627
@group
1628
# Second form
1629
convert IMAGE \
1630
\( \
1631
\( IMAGE -threshold LOWER-CUTOFF \) \
1632
\( IMAGE -threshold UPPER-CUTOFF -negate \) \
1633
-compose multiply -composite \
1634
\) \
1635
-compose copy_opacity -composite \
1636
MASKED-IMAGE
1637
@end group
1638
@end example
1639
1640
(Transforming some or all input images as shown in the above examples
1641
gives the user more flexibility because the thresholds can be chosen
1642
for each image individually.)
1643
1644
The third form specifies projection operators as in
1645
option@tie{}@option{--gray-projector} for the @var{LOWER-CUTOFF} and
1646
@var{UPPER-CUTOFF} thresholds.
1647
1648
This option can be helpful if the user wants to exclude underexposed
1649
or overexposed pixels from the fusing process in @emph{all} of the
1650
input images. The values of @var{LOWER-CUTOFF} and @var{UPPER-CUTOFF}
1651
as well as the gray-scale projector determine which pixels are
1652
considered ``underexposed'' or ``overexposed''. As any change of the
1653
exposure-weight curve this option changes the brightness of the
1654
resulting image: increasing @var{LOWER-CUTOFF} lightens the final
1655
image and lowering @var{UPPER-CUTOFF} darkens it.
1656
1657
Defaults: @value{src::default-exposure-lower-cutoff} for
1658
@var{LOWER-CUTOFF} and @value{src::default-exposure-upper-cutoff} for
1659
@var{UPPER-CUTOFF}, that is, all pixels' values are weighted according
1660
to the ``uncut'' exposure-weight curve.
1661
1662
Append a @samp{%} to specify the cutoff relative to the maximum pixel
1663
value in the source image (for example 255 or 65535).
1664
1665
@ref{Figure:exposure-cutoff} shows an example.
1666
1667
The gray-scale projectors @var{LOWER-PROJECTOR} and
1668
@var{UPPER-PROJECTOR} default to
1669
@samp{@value{src::default-exposure-lower-cutoff-projector}} and
1670
@samp{@value{src::default-exposure-upper-cutoff-projector}}, which are
1671
usually the best choices for effective cutoff operations on the
1672
respective ends.
1673
1674
@float Figure,Figure:exposure-cutoff
1675
@vimage{exposure-cutoff}
1676
1677
@caption{Exposure weight, a Gaussian with @var{Mu} = 0.5 and @var{Sigma} = 0.2 submitted to an exposure-cutoff of @var{LOWER-CUTOFF} = 5% and @var{UPPER-CUTOFF} = 97%.}
1678
1679
@shortcaption{Exposure cutoff function}
1680
@end float
1681
1682
Note that the application of the respective cutoffs is completely
1683
independent of the actual shape of the exposure weight function.
1684
1685
If a set of images stubbornly refuses to ``react'' to this option,
1686
look at their histograms to verify the cutoff actually falls into
1687
populated ranges of the histograms. In the absence of an image
1688
manipulation program like @uref{http://@/www.gimp.org/, The Gimp},
1689
@uref{http://@/www.imagemagick.org/, ImageMagick} (@pxref{Helpful
1690
Programs}) can be used to generate
1691
@uref{http://@/www.imagemagick.org/@/Usage/@/files/@/#histogram,
1692
histograms}, like, for example,
1693
1694
@example
1695
@group
1696
convert -define histogram:unique-colors=false \
1697
IMAGE histogram:- | \
1698
display
1699
@end group
1700
@end example
1701
1702
@item --gray-projector=@var{PROJECTOR}
1703
@opindex --gray-projector
1704
@cindex gray projector
1705
1706
Use gray projector@tie{}@var{PROJECTOR} for conversion of
1707
@acronym{RGB} images to grayscale:
1708
@ifinfo
1709
@math{(R, G, B) --> Y.}
1710
@end ifinfo
1711
@html
1712
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
1713
<mrowinline>
1714
<mfencedinline>
1715
<mi>R</mi>
1716
<mi>G</mi>
1717
<mi>B</mi>
1718
</mfencedinline>
1719
<mo>→</mo>
1720
<mi>Y</mi>
1721
<mtext>.</mtext>
1722
</mrowinline>
1723
</mathinline>
1724
@end html
1725
@tex
1726
$(R, G, B) \rightarrow Y.$
1727
@end tex
1728
@docbook
1729
<informalequation>
1730
<mml:math>
1731
<mml:lambda>
1732
<mml:bvar>
1733
<mml:vector>
1734
<mml:ci>R</mml:ci>
1735
<mml:ci>G</mml:ci>
1736
<mml:ci>B</mml:ci>
1737
</mml:vector>
1738
</mml:bvar>
1739
<mml:ci>Y</mml:ci>
1740
</mml:lambda>
1741
</mml:math>
1742
</informalequation>
1743
@end docbook
1744
1745
In version@tie{}@value{VERSION} of Enfuse, the option is effective for
1746
exposure weighting and local contrast weighting. Default:
1747
@samp{average}.
1748
1749
Valid values for @var{PROJECTOR} are:
1750
1751
@table @code
1752
@item anti-value
1753
@cindex gray projector, @samp{anti-value}
1754
@cindex @samp{anti-value} gray projector
1755
Do the opposite of the @samp{value} projector: take the minimum of all
1756
color channels.
1757
@ifinfo
1758
@display
1759
@math{Y = min(R, G, B)}
1760
@end display
1761
@end ifinfo
1762
@html
1763
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
1764
<mrow>
1765
<mi>Y</mi>
1766
<mo>=</mo>
1767
<mrow>
1768
<mo>min</mo>
1769
<mo>⁡</mo>
1770
<mfenced>
1771
<mi>R</mi>
1772
<mi>G</mi>
1773
<mi>B</mi>
1774
</mfenced>
1775
</mrow>
1776
</mrow>
1777
</math>
1778
@end html
1779
@tex
1780
$$
1781
Y = \min(R, G, B)
1782
$$
1783
@end tex
1784
@docbook
1785
<informalequation>
1786
<mml:math>
1787
<mml:reln>
1788
<mml:eq/>
1789
<mml:ci>Y</mml:ci>
1790
<mml:apply>
1791
<mml:min/>
1792
<mml:ci>R</mml:ci>
1793
<mml:ci>G</mml:ci>
1794
<mml:ci>B</mml:ci>
1795
</mml:apply>
1796
</mml:reln>
1797
</mml:math>
1798
</informalequation>
1799
@end docbook
1800
1801
This projector can be useful when exposure weighing while employing a
1802
lower cutoff (see option@tie{}@option{--exposure-cutoff}) to reduce
1803
the noise in the fused image.
1804
1805
@item average
1806
@cindex gray projector, @samp{average}
1807
@cindex @samp{average} gray projector
1808
Average red, green, and blue channel with equal weights. This is the
1809
default, and it often is a good projector for @math{gamma = 1} data.
1810
@ifinfo
1811
@display
1812
@math{Y = (R + G + B) / 3}
1813
@end display
1814
@end ifinfo
1815
@html
1816
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
1817
<mrow>
1818
<mi>Y</mi>
1819
<mo>=</mo>
1820
<mfrac>
1821
<mrow>
1822
<mi>R</mi>
1823
<mo>+</mo>
1824
<mi>G</mi>
1825
<mo>+</mo>
1826
<mi>B</mi>
1827
</mrow>
1828
<mn>3</mn>
1829
</mfrac>
1830
</mrow>
1831
</math>
1832
@end html
1833
@tex
1834
$$
1835
Y = {R + G + B \over 3}
1836
$$
1837
@end tex
1838
@docbook
1839
<informalequation>
1840
<mml:math>
1841
<mml:reln>
1842
<mml:eq/>
1843
<mml:ci>Y</mml:ci>
1844
<mml:apply other='display="scriptstyle"'>
1845
<mml:divide/>
1846
<mml:apply>
1847
<mml:plus/>
1848
<mml:ci>R</mml:ci>
1849
<mml:ci>G</mml:ci>
1850
<mml:ci>B</mml:ci>
1851
</mml:apply>
1852
<mml:cn>3</mml:cn>
1853
</mml:apply>
1854
</mml:reln>
1855
</mml:math>
1856
</informalequation>
1857
@end docbook
1858
1859
@item channel-mixer:@var{RED-WEIGHT}:@var{GREEN-WEIGHT}:@var{BLUE-WEIGHT}
1860
@cindex gray projector, @samp{channel-mixer}
1861
@cindex @samp{channel-mixer} gray projector
1862
Weight the channels as given.
1863
@ifinfo
1864
@display
1865
@math{Y = RED-WEIGHT * R + GREEN-WEIGHT * G + BLUE-WEIGHT * B}
1866
@end display
1867
@end ifinfo
1868
@html
1869
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
1870
<mrow>
1871
<mi>Y</mi>
1872
<mo>=</mo>
1873
<mrow>
1874
<mi mathvariant="italic">RED-WEIGHT</mi>
1875
<mo>×</mo>
1876
<mi>R</mi>
1877
</mrow>
1878
<mo>+</mo>
1879
<mrow>
1880
<mi mathvariant="italic">GREEN-WEIGHT</mi>
1881
<mo>×</mo>
1882
<mi>G</mi>
1883
</mrow>
1884
<mo>+</mo>
1885
<mrow>
1886
<mi mathvariant="italic">BLUE-WEIGHT</mi>
1887
<mo>×</mo>
1888
<mi>B</mi>
1889
</mrow>
1890
</mrow>
1891
</math>
1892
@end html
1893
@tex
1894
$$
1895
\eqalign{Y \quad = \quad
1896
& \mathit{RED-WEIGHT} \times R \; + \cr
1897
& \mathit{GREEN-WEIGHT} \times G \; + \cr
1898
& \mathit{BLUE-WEIGHT} \times B \cr}
1899
$$
1900
@end tex
1901
@docbook
1902
<informalequation>
1903
<mml:math>
1904
<mml:reln>
1905
<mml:eq/>
1906
<mml:ci>Y</mml:ci>
1907
<mml:apply>
1908
<mml:plus/>
1909
<mml:apply>
1910
<mml:times/>
1911
<mml:csymbol>
1912
<mml:mi mathvariant="italic">RED-WEIGHT</mml:mi>
1913
</mml:csymbol>
1914
<mml:ci>R</mml:ci>
1915
</mml:apply>
1916
<mml:apply>
1917
<mml:times/>
1918
<mml:csymbol>
1919
<mml:mi mathvariant="italic">GREEN-WEIGHT</mml:mi>
1920
</mml:csymbol>
1921
<mml:ci>G</mml:ci>
1922
</mml:apply>
1923
<mml:apply>
1924
<mml:times/>
1925
<mml:csymbol>
1926
<mml:mi mathvariant="italic">BLUE-WEIGHT</mml:mi>
1927
</mml:csymbol>
1928
<mml:ci>B</mml:ci>
1929
</mml:apply>
1930
</mml:apply>
1931
</mml:reln>
1932
</mml:math>
1933
</informalequation>
1934
@end docbook
1935
1936
The weights are automatically normalized to one, so
1937
1938
@example
1939
--gray-projector=channel-mixer:0.25:0.5:0.25
1940
--gray-projector=channel-mixer:1:2:1
1941
--gray-projector=channel-mixer:25:50:25
1942
@end example
1943
1944
all define the same mixer configuration.
1945
1946
The three weights @var{RED-WEIGHT}, @var{GREEN-WEIGHT}, and
1947
@var{BLUE-WEIGHT} define the relative weight of the respective color
1948
channel. The sum of all weights is normalized to one.
1949
1950
@item l-star
1951
@cindex gray projector, @samp{l-star}
1952
@cindex @samp{l-star} gray projector
1953
@cindex RGB-L*a*b* conversion
1954
@cindex conversion, RGB-L*a*b*
1955
Use the L-channel of the L*a*b*-conversion of the image as its
1956
grayscale representation. This is a useful projector for gamma = 1
1957
data. It reveals minute contrast variations even in the shadows and
1958
the highlights. This projector is computationally expensive. Compare
1959
with @samp{pl-star}, which is intended for gamma-corrected images.
1960
1961
See @uref{http://@/en.wikipedia.org/@/wiki/@/Lab_@/color_@/space,
1962
Wikipedia} for a detailed description of the @acronym{Lab}@tie{}color
1963
space.
1964
1965
@item lightness
1966
@cindex gray projector, @samp{lightness}
1967
@cindex @samp{lightness} gray projector
1968
Compute the lightness of each @acronym{RGB} pixel as in an
1969
Hue-Saturation-Lightness (@acronym{HSL}) conversion of the image.
1970
@ifinfo
1971
@display
1972
@math{Y = (max(R, G, B) + min(R, G, B)) / 2}
1973
@end display
1974
@end ifinfo
1975
@html
1976
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
1977
<mrow>
1978
<mi>Y</mi>
1979
<mo>=</mo>
1980
<mfrac>
1981
<mrow>
1982
<mrow>
1983
<mo>max</mo>
1984
<mo>⁡</mo>
1985
<mfenced>
1986
<mi>R</mi>
1987
<mi>G</mi>
1988
<mi>B</mi>
1989
</mfenced>
1990
</mrow>
1991
<mo>+</mo>
1992
<mrow>
1993
<mo>min</mo>
1994
<mo>⁡</mo>
1995
<mfenced>
1996
<mi>R</mi>
1997
<mi>G</mi>
1998
<mi>B</mi>
1999
</mfenced>
2000
</mrow>
2001
</mrow>
2002
<mn>2</mn>
2003
</mfrac>
2004
</mrow>
2005
</math>
2006
@end html
2007
@tex
2008
$$
2009
Y = {\max(R, G, B) + \min(R, G, B) \over 2}
2010
$$
2011
@end tex
2012
@docbook
2013
<informalequation>
2014
<mml:math>
2015
<mml:reln>
2016
<mml:eq/>
2017
<mml:ci>Y</mml:ci>
2018
<mml:apply>
2019
<mml:divide/>
2020
<mml:apply>
2021
<mml:plus/>
2022
<mml:apply>
2023
<mml:max/>
2024
<mml:ci>R</mml:ci>
2025
<mml:ci>G</mml:ci>
2026
<mml:ci>B</mml:ci>
2027
</mml:apply>
2028
<mml:apply>
2029
<mml:min/>
2030
<mml:ci>R</mml:ci>
2031
<mml:ci>G</mml:ci>
2032
<mml:ci>B</mml:ci>
2033
</mml:apply>
2034
</mml:apply>
2035
<mml:cn>2</mml:cn>
2036
</mml:apply>
2037
</mml:reln>
2038
</mml:math>
2039
</informalequation>
2040
@end docbook
2041
2042
@item luminance
2043
@cindex gray projector, @samp{luminance}
2044
@cindex @samp{luminance} gray projector
2045
Use the weighted average of the @acronym{RGB} pixel's channels as
2046
defined by @acronym{CIE} (``Commission Internationale de
2047
l'@'Eclairage'') and the @acronym{JPEG} standard.
2048
@ifinfo
2049
@display
2050
@math{Y = 0.30 * R + 0.59 * G + 0.11 * B}
2051
@end display
2052
@end ifinfo
2053
@html
2054
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
2055
<mrow>
2056
<mi>Y</mi>
2057
<mo>=</mo>
2058
<mrow>
2059
<mn>0.30</mn>
2060
<mo>×</mo>
2061
<mi>R</mi>
2062
</mrow>
2063
<mo>+</mo>
2064
<mrow>
2065
<mn>0.59</mn>
2066
<mo>×</mo>
2067
<mi>G</mi>
2068
</mrow>
2069
<mo>+</mo>
2070
<mrow>
2071
<mn>0.11</mn>
2072
<mo>×</mo>
2073
<mi>B</mi>
2074
</mrow>
2075
</mrow>
2076
</math>
2077
@end html
2078
@tex
2079
$$
2080
Y = 0.30 \times R + 0.59 \times G + 0.11 \times B
2081
$$
2082
@end tex
2083
@docbook
2084
<informalequation>
2085
<mml:math>
2086
<mml:reln>
2087
<mml:eq/>
2088
<mml:ci>Y</mml:ci>
2089
<mml:apply>
2090
<mml:plus/>
2091
<mml:apply>
2092
<mml:times/>
2093
<mml:cn type="real">0.30</mml:cn>
2094
<mml:ci>R</mml:ci>
2095
</mml:apply>
2096
<mml:apply>
2097
<mml:times/>
2098
<mml:cn type="real">0.59</mml:cn>
2099
<mml:ci>G</mml:ci>
2100
</mml:apply>
2101
<mml:apply>
2102
<mml:times/>
2103
<mml:cn type="real">0.11</mml:cn>
2104
<mml:ci>B</mml:ci>
2105
</mml:apply>
2106
</mml:apply>
2107
</mml:reln>
2108
</mml:math>
2109
</informalequation>
2110
@end docbook
2111
2112
@item pl-star
2113
@cindex gray projector, @samp{pl-star}
2114
@cindex @samp{pl-star} gray projector
2115
@cindex RGB'-L*a*b* conversion
2116
@cindex conversion, RGB'-L*a*b*
2117
Use the L-channel of the L*a*b*-conversion of the image as its
2118
grayscale representation. This is a useful projector for
2119
gamma-corrected data. It reveals minute contrast variations even in
2120
the shadows and the highlights. This projector is computationally
2121
expensive. Compare with @samp{l-star}, which is intended for gamma =
2122
1 images.
2123
2124
See @uref{http://@/en.wikipedia.org/@/wiki/@/Lab_@/color_@/space,
2125
Wikipedia} for a detailed description of the @acronym{Lab}@tie{}color
2126
space.
2127
2128
@item value
2129
@cindex gray projector, @samp{value}
2130
@cindex @samp{value} gray projector
2131
Take the Value-channel of the Hue-Saturation-Value (@acronym{HSV})
2132
conversion of the image.
2133
@ifinfo
2134
@display
2135
@math{Y = max(R, G, B)}
2136
@end display
2137
@end ifinfo
2138
@html
2139
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
2140
<mrow>
2141
<mi>Y</mi>
2142
<mo>=</mo>
2143
<mrow>
2144
<mo>max</mo>
2145
<mo>⁡</mo>
2146
<mfenced>
2147
<mi>R</mi>
2148
<mi>G</mi>
2149
<mi>B</mi>
2150
</mfenced>
2151
</mrow>
2152
</mrow>
2153
</math>
2154
@end html
2155
@tex
2156
$$
2157
Y = \max(R, G, B)
2158
$$
2159
@end tex
2160
@docbook
2161
<informalequation>
2162
<mml:math>
2163
<mml:reln>
2164
<mml:eq/>
2165
<mml:ci>Y</mml:ci>
2166
<mml:apply>
2167
<mml:max/>
2168
<mml:ci>R</mml:ci>
2169
<mml:ci>G</mml:ci>
2170
<mml:ci>B</mml:ci>
2171
</mml:apply>
2172
</mml:reln>
2173
</mml:math>
2174
</informalequation>
2175
@end docbook
2176
@end table
2177
2178
@item --hard-mask
2179
@opindex --hard-mask
2180
2181
Force hard blend masks on the finest scale. This is the opposite flag
2182
of @option{--soft-mask}.
2183
2184
This blending mode avoids averaging of fine details (only) at the
2185
expense of increasing the noise. However it considerably improves the
2186
sharpness of focus stacks. Blending with hard masks has only proven
2187
useful with focus stacks.
2188
2189
See also @ref{Fusion Options, Option --contrast-weight} and
2190
@option{--contrast-window-size} above.
2191
2192
@item --load-masks
2193
@itemx --load-masks=@var{SOFT-MASK-TEMPLATE}
2194
@itemx --load-masks=@var{SOFT-MASK-TEMPLATE}:@var{HARD-MASK-TEMPLATE}
2195
@opindex --load-masks
2196
2197
Load masks from images instead of computing them.
2198
2199
The masks have to be a grayscale images.
2200
2201
@cindex mask, loading
2202
First form: Load all soft-weight masks from files that were previously
2203
saved with option@tie{}@option{--save-masks}. If
2204
option@tie{}@option{--hard-mask} is effective only load hard masks.
2205
The defaults are @file{@value{src::default-soft-mask-template}} and
2206
@file{@value{src::default-hard-mask-template}}.
2207
@cindex filename template
2208
@cindex mask, filename template
2209
In the second form, @var{SOFT-MASK-TEMPLATE} defines the names of the
2210
soft-mask files. In the third form, @var{HARD-MASK-TEMPLATE}
2211
additionally defines the names of the hard-mask files. See
2212
option@tie{}@option{--save-masks} below for the description of mask
2213
templates.
2214
2215
Options@tie{}@option{--load-masks} and @option{--save-masks} are
2216
mutually exclusive.
2217
2218
@item --save-masks
2219
@itemx --save-masks=@var{SOFT-MASK-TEMPLATE}
2220
@itemx --save-masks=@var{SOFT-MASK-TEMPLATE}:@var{HARD-MASK-TEMPLATE}
2221
@opindex --save-masks
2222
@cindex mask, save
2223
@cindex save mask
2224
Save the generated weight masks to image files.
2225
2226
First form: Save all soft-weight masks in files. If
2227
option@tie{}@option{--hard-mask} is effective also save the hard masks.
2228
The defaults are @file{@value{src::default-soft-mask-template}} and
2229
@file{@value{src::default-hard-mask-template}}.
2230
@cindex filename template
2231
@cindex mask, filename template
2232
In the second form, @var{SOFT-MASK-TEMPLATE} defines the names of the
2233
soft-mask files. In the third form, @var{HARD-MASK-TEMPLATE}
2234
additionally defines the names of the hard-mask files.
2235
2236
@cindex save mask, only
2237
@cindex only save mask
2238
Enfuse will stop after saving all masks unless
2239
option@tie{}@option{--output} is given, too. With both options given,
2240
this is, @option{--save-masks} and @option{--output}, Enfuse saves all
2241
masks and then proceeds to fuse the output image.
2242
2243
Both @var{SOFT-MASK-TEMPLATE} and @var{HARD-MASK-TEMPLATE} define
2244
templates that are expanded for each mask file. In a template a
2245
percent sign (@samp{%}) introduces a variable part. All other
2246
characters are copied literally. Lowercase letters refer to the name
2247
of the respective input file, whereas uppercase ones refer to the name
2248
of the output file (@pxref{Common Options}).
2249
@ref{Table:mask-template-characters} lists all variables.
2250
2251
A fancy mask filename template could look like this:
2252
2253
@example
2254
%D/soft-mask-%02n-%f.viff
2255
@end example
2256
2257
It puts the mask files into the same directory as the output file
2258
(@samp{%D}), generates a two-digit index (@samp{%02n}) to keep the
2259
mask files nicely sorted, and decorates the mask filename with the
2260
name of the associated input file (@samp{%f}) for easy recognition.
2261
2262
@item --soft-mask
2263
@opindex --soft-mask
2264
2265
Consider all masks when fusing. This is the default.
2266
@end table
2267
2268
@c The extra <para>s fix another stupid Texinfo problem with DocBook.
2269
@docbook
2270
<para>
2271
@end docbook
2272
Options@tie{}@option{--save-masks} and @option{--load-masks} are
2273
mutually exclusive.
2274
@docbook
2275
</para>
2276
@end docbook
2277
2278
@page
2279
2280
@include mask-template-characters.texi
2281
2282
@node Option Delimiters
2283
@section Option Delimiters
2284
@cindex option delimiters
2285
@cindex delimiters, option
2286
2287
Enfuse allows the arguments supplied to the program's options to be
2288
separated by different separators. The online documentation and this
2289
manual, however, exclusively use the colon @samp{:} in every syntax
2290
definition and in all examples.
2291
2292
@need 500
2293
@noindent
2294
@strong{Numeric Arguments}
2295
2296
Valid delimiters are the the semicolon @samp{;}, the colon @samp{:},
2297
and the slash @samp{/}. All delimiters may be mixed within any
2298
option that takes numeric arguments.
2299
2300
@noindent
2301
Examples:
2302
2303
@table @samp
2304
@item --contrast-edge-scale=0.667:6.67:3.5
2305
Separate all arguments with colons.
2306
2307
@item --contrast-edge-scale=0.667;6.67;3.5
2308
Use semi-colons.
2309
2310
@item --contrast-edge-scale=0.667;6.67/3.5
2311
Mix semicolon and slash in weird ways.
2312
2313
@item --entropy-cutoff=3%/99%
2314
All delimiters also work in conjunction with percentages.
2315
2316
@item --gray-projector=channel-mixer:3/6/1
2317
Separate arguments with a colon and two slashes.
2318
2319
@item --gray-projector=channel-mixer/30;60:10
2320
Go wild and Enfuse will understand.
2321
@end table
2322
2323
@need 500
2324
@noindent
2325
@strong{Filename Arguments}
2326
2327
Here, the accepted delimiters are @samp{,}, @samp{;}, and @samp{:}.
2328
Again, all delimiters may be mixed within any option that has filename
2329
arguments.
2330
2331
@noindent
2332
Examples:
2333
2334
@table @samp
2335
@item --save-masks=soft-mask-%03i.tif:hard-mask-03%i.tif
2336
Separate all arguments with colons.
2337
2338
@item --save-masks=%d/soft-%n.tif,%d/hard-%n.tif
2339
Use a comma.
2340
@end table
2341
2342
2343
@node Color Profiles
2344
@chapter Color Profiles
2345
@cindex profile, @acronym{ICC}
2346
@cindex @acronym{ICC} profile
2347
@cindex color profile
2348
2349
@include color-profiles.texi
2350
2351
2352
@node Weighting Functions
2353
@chapter Weighting Functions
2354
@cindex weighting functions
2355
2356
As has been noted in the Overview (@pxref{Overview}), Enfuse supports
2357
four different types of weighting. The following subsections describe
2358
the concept of weighting and all weighting functions in detail.
2359
2360
@menu
2361
* Weighting Pixels:: General concept of weighting pixels
2362
* Exposure Weighting:: Weighting by exposure
2363
* Saturation Weighting:: Weighting by saturation
2364
* Local Contrast Weighting:: Weighting by local contrast
2365
* Local Entropy Weighting:: Weighting by local entropy
2366
@end menu
2367
2368
2369
@node Weighting Pixels
2370
@section Weighting Pixels
2371
@cindex weighting, general concept of
2372
2373
Image fusion maps each pixel@tie{}@math{P(i, x, y)} of every input
2374
image @math{i} to a single pixel@tie{}@math{Q(x, y)} in the output
2375
image:
2376
@ifinfo
2377
@display
2378
@math{P(i, x, y) --> Q(x, y),}
2379
@end display
2380
@end ifinfo
2381
@html
2382
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
2383
<mrow>
2384
<mrow>
2385
<mi>P</mi>
2386
<mfenced>
2387
<mi>i</mi>
2388
<mi>x</mi>
2389
<mi>y</mi>
2390
</mfenced>
2391
</mrow>
2392
<mo>→</mo>
2393
<mrow>
2394
<mi>Q</mi>
2395
<mfenced>
2396
<mi>x</mi>
2397
<mi>y</mi>
2398
</mfenced>
2399
</mrow>
2400
<mtext>,</mtext>
2401
</mrow>
2402
</math>
2403
@end html
2404
@tex
2405
$$
2406
P(i, x, y) \rightarrow Q(x, y),
2407
$$
2408
@end tex
2409
@docbook
2410
<informalequation>
2411
<mml:math>
2412
<mml:lambda>
2413
<mml:bvar>
2414
<mml:apply>
2415
<mml:ci>P</mml:ci>
2416
<mml:ci>i</mml:ci>
2417
<mml:ci>x</mml:ci>
2418
<mml:ci>y</mml:ci>
2419
</mml:apply>
2420
</mml:bvar>
2421
<mml:apply>
2422
<mml:ci>Q</mml:ci>
2423
<mml:ci>x</mml:ci>
2424
<mml:ci>y</mml:ci>
2425
</mml:apply>
2426
</mml:lambda>
2427
</mml:math>
2428
</informalequation>
2429
@end docbook
2430
2431
@noindent
2432
where @math{x} runs from 1 to the common width of the images, @math{y}
2433
from 1 to the common height, and @math{i} from 1 to the number of
2434
input images@tie{}@math{n}.
2435
2436
@macro equationW{}
2437
@ifnotdocbook
2438
@ifnottex
2439
(W)
2440
@end ifnottex
2441
@end ifnotdocbook
2442
@tex
2443
(W)%
2444
@end tex
2445
@docbook
2446
<xref linkend="equ:pixel-weighting-function"/>
2447
@end docbook
2448
@end macro
2449
2450
Enfuse allows for weighting the contribution of each @math{P(i, x, y)}
2451
to the final @math{Q(x, y)}:
2452
@ifinfo
2453
@display
2454
@math{w(P(1, x, y)) * P(1, x, y) +
2455
... +
2456
w(P(n, x, y)) * P(n, x, y)
2457
--> Q(x, y),}@w{ }@equationW{}
2458
@end display
2459
@end ifinfo
2460
@html
2461
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
2462
<mrow>
2463
<mrow>
2464
<mi>w</mi>
2465
<mo>⁡</mo>
2466
<mrow>
2467
<mo>(</mo>
2468
<mrow>
2469
<mi>P</mi>
2470
<mfenced>
2471
<mi>1</mi>
2472
<mi>x</mi>
2473
<mi>y</mi>
2474
</mfenced>
2475
</mrow>
2476
<mo>)</mo>
2477
</mrow>
2478
<mo>×</mo>
2479
<mrow>
2480
<mi>P</mi>
2481
<mfenced>
2482
<mi>1</mi>
2483
<mi>x</mi>
2484
<mi>y</mi>
2485
</mfenced>
2486
</mrow>
2487
<mo>+</mo>
2488
<mo>...</mo>
2489
<mo>+</mo>
2490
<mi>w</mi>
2491
<mo>⁡</mo>
2492
<mrow>
2493
<mo>(</mo>
2494
<mrow>
2495
<mi>P</mi>
2496
<mfenced>
2497
<mi>n</mi>
2498
<mi>x</mi>
2499
<mi>y</mi>
2500
</mfenced>
2501
</mrow>
2502
<mo>)</mo>
2503
</mrow>
2504
<mo>×</mo>
2505
<mrow>
2506
<mi>P</mi>
2507
<mfenced>
2508
<mi>n</mi>
2509
<mi>x</mi>
2510
<mi>y</mi>
2511
</mfenced>
2512
</mrow>
2513
</mrow>
2514
<mo>→</mo>
2515
<mrow>
2516
<mi>Q</mi>
2517
<mfenced>
2518
<mi>i</mi>
2519
<mi>x</mi>
2520
<mi>y</mi>
2521
</mfenced>
2522
</mrow>
2523
<mtext>,</mtext>
2524
<mspace width="4em"/>
2525
<mtext>@equationW{}</mtext>
2526
</mrow>
2527
</math>
2528
@end html
2529
@tex
2530
$$
2531
w(P(1, x, y)) P(1, x, y) + \ldots + w(P(n, x, y)) P(n, x, y)
2532
\rightarrow
2533
Q(x, y),\hskip4em\hbox{@equationW{}}
2534
$$
2535
@end tex
2536
@docbook
2537
<equation id="equ:pixel-weighting-function">
2538
<title>Pixel Weighting Function</title>
2539
<mml:math>
2540
<mml:lambda>
2541
<mml:bvar>
2542
<mml:apply>
2543
<mml:plus/>
2544
<mml:apply>
2545
<mml:times/>
2546
<mml:apply>
2547
<mml:ci>w</mml:ci>
2548
<mml:apply>
2549
<mml:ci>P</mml:ci>
2550
<mml:cn>1</mml:cn>
2551
<mml:ci>x</mml:ci>
2552
<mml:ci>y</mml:ci>
2553
</mml:apply>
2554
</mml:apply>
2555
<mml:apply>
2556
<mml:ci>P</mml:ci>
2557
<mml:cn>1</mml:cn>
2558
<mml:ci>x</mml:ci>
2559
<mml:ci>y</mml:ci>
2560
</mml:apply>
2561
</mml:apply>
2562
<mml:mo>...</mml:mo>
2563
<mml:apply>
2564
<mml:times/>
2565
<mml:apply>
2566
<mml:ci>w</mml:ci>
2567
<mml:apply>
2568
<mml:ci>P</mml:ci>
2569
<mml:ci>n</mml:ci>
2570
<mml:ci>x</mml:ci>
2571
<mml:ci>y</mml:ci>
2572
</mml:apply>
2573
</mml:apply>
2574
<mml:apply>
2575
<mml:ci>P</mml:ci>
2576
<mml:ci>n</mml:ci>
2577
<mml:ci>x</mml:ci>
2578
<mml:ci>y</mml:ci>
2579
</mml:apply>
2580
</mml:apply>
2581
</mml:apply>
2582
</mml:bvar>
2583
<mml:apply>
2584
<mml:ci>Q</mml:ci>
2585
<mml:ci>x</mml:ci>
2586
<mml:ci>y</mml:ci>
2587
</mml:apply>
2588
</mml:lambda>
2589
</mml:math>
2590
</equation>
2591
@end docbook
2592
2593
@noindent
2594
where
2595
2596
@itemize
2597
@item
2598
each @math{w} is non-negative to yield a physical intensity and
2599
2600
@item
2601
the sum of all @math{w} is one to leave the total intensity unchanged.
2602
@end itemize
2603
2604
@noindent
2605
The pixel weights@tie{}@math{w} themselves are weighted sums with the
2606
same constraints
2607
@ifinfo
2608
@display
2609
@math{w(P) = w_exp * f_exp(P) +
2610
w_sat * f_sat(P) +
2611
w_cont * f_cont(P, r_cont) +
2612
w_ent * f_ent(P, r_ent),}
2613
@end display
2614
2615
@noindent
2616
where we have abbreviated @math{P(i, x, y)} to @math{P} for
2617
simplicity. The user defines the constants@tie{}@math{w_exp},
2618
@math{w_sat}, @math{w_cont}, and @math{w_ent} with the options
2619
@option{--exposure-weight}, @option{--saturation-weight},
2620
@option{--contrast-weight}, and @option{--entropy-weight}. The
2621
functions@tie{}@math{f_exp}, @math{f_sat}, @math{f_cont}, and
2622
@math{f_ent} along with the window sizes@tie{}@math{r_cont} and
2623
@math{r_ent} are explained in the next sections.
2624
@end ifinfo
2625
@html
2626
</p>
2627
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
2628
<mtable>
2629
<mtr>
2630
<mtd>
2631
<mi>w</mi>
2632
<mo>⁡</mo>
2633
<mrow>
2634
<mo>(</mo>
2635
<mi>P</mi>
2636
<mo>)</mo>
2637
</mrow>
2638
</mtd>
2639
<mtd>
2640
<mo>=</mo>
2641
</mtd>
2642
<mtd>
2643
<msub>
2644
<mi>w</mi>
2645
<mtext>exp</mtext>
2646
</msub>
2647
<mo>×</mo>
2648
<mrow>
2649
<msub>
2650
<mi>f</mi>
2651
<mtext>exp</mtext>
2652
</msub>
2653
<mo>⁡</mo>
2654
<mrow>
2655
<mo>(</mo>
2656
<mi>P</mi>
2657
<mo>)</mo>
2658
</mrow>
2659
<mo>+</mo>
2660
</mrow>
2661
</mtd>
2662
</mtr>
2663
<mtr>
2664
<mtd></mtd>
2665
<mtd></mtd>
2666
<mtd>
2667
<msub>
2668
<mi>w</mi>
2669
<mtext>sat</mtext>
2670
</msub>
2671
<mo>×</mo>
2672
<mrow>
2673
<msub>
2674
<mi>f</mi>
2675
<mtext>sat</mtext>
2676
</msub>
2677
<mo>⁡</mo>
2678
<mrow>
2679
<mo>(</mo>
2680
<mi>P</mi>
2681
<mo>)</mo>
2682
</mrow>
2683
<mo>+</mo>
2684
</mrow>
2685
</mtd>
2686
</mtr>
2687
<mtr>
2688
<mtd></mtd>
2689
<mtd></mtd>
2690
<mtd>
2691
<msub>
2692
<mi>w</mi>
2693
<mtext>cont</mtext>
2694
</msub>
2695
<mo>×</mo>
2696
<mrow>
2697
<msub>
2698
<mi>f</mi>
2699
<mtext>cont</mtext>
2700
</msub>
2701
<mo>⁡</mo>
2702
<mfenced>
2703
<mi>P</mi>
2704
<msub>
2705
<mi>r</mi>
2706
<mtext>cont</mtext>
2707
</msub>
2708
</mfenced>
2709
</mrow>
2710
<mo>+</mo>
2711
</mtd>
2712
</mtr>
2713
<mtr>
2714
<mtd></mtd>
2715
<mtd></mtd>
2716
<mtd>
2717
<msub>
2718
<mi>w</mi>
2719
<mtext>ent</mtext>
2720
</msub>
2721
<mo>×</mo>
2722
<mrow>
2723
<msub>
2724
<mi>f</mi>
2725
<mtext>ent</mtext>
2726
</msub>
2727
<mo>⁡</mo>
2728
<mfenced>
2729
<mi>P</mi>
2730
<msub>
2731
<mi>r</mi>
2732
<mtext>ent</mtext>
2733
</msub>
2734
</mfenced>
2735
</mrow>
2736
</mtd>
2737
</mtr>
2738
</mtable>
2739
</math>
2740
2741
<p>where we have abbreviated
2742
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2743
<mi>P</mi> <mrowinline> <mo>(</mo> <mi>i</mi> <mo>,</mo> <mi>x</mi> <mo>,</mo>
2744
<mi>y</mi> <mo>)</mo> </mrowinline> </mathinline> to
2745
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2746
<mi>P</mi> </mathinline> for simplicity. The user defines the
2747
constants <mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2748
<msubinline> <mi>w</mi> <mtext>exp</mtext> </msubinline> </mathinline>,
2749
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2750
<msubinline> <mi>w</mi> <mtext>sat</mtext> </msubinline> </mathinline>,
2751
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2752
<msubinline> <mi>w</mi> <mtext>cont</mtext> </msubinline> </mathinline>, and
2753
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2754
<msubinline> <mi>w</mi> <mtext>ent</mtext> </msubinline> </mathinline> with the options
2755
`<tt>--exposure-weight</tt>', `<tt>--saturation-weight</tt>',
2756
`<tt>--contrast-weight</tt>', and `<tt>--entropy-weight</tt>'
2757
respectively. The
2758
functions <mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2759
<msubinline> <mi>f</mi> <mtext>exp</mtext> </msubinline> </mathinline>,
2760
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2761
<msubinline> <mi>f</mi> <mtext>sat</mtext> </msubinline> </mathinline>,
2762
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2763
<msubinline> <mi>f</mi> <mtext>cont</mtext> </msubinline> </mathinline>, and
2764
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2765
<msubinline> <mi>f</mi> <mtext>ent</mtext> </msubinline> </mathinline> along with the window
2766
sizes <mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2767
<msubinline> <mi>r</mi> <mtext>cont</mtext> </msubinline> </mathinline> and
2768
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
2769
<msubinline> <mi>r</mi> <mtext>ent</mtext> </msubinline> </mathinline> are explained in
2770
the next sections.</p><p>
2771
@end html
2772
@tex
2773
$$
2774
\eqalign{w(P) \quad = \quad
2775
& w_{\mathrm{exp}} \; f_{\mathrm{exp}}(P) + \cr
2776
& w_{\mathrm{sat}} \; f_{\mathrm{sat}}(P) + \cr
2777
& w_{\mathrm{cont}} \; f_{\mathrm{cont}}(P, r_{\mathrm{cont}}) + \cr
2778
& w_{\mathrm{ent}} \; f_{\mathrm{ent}}(P, r_{\mathrm{ent}}), \cr}
2779
$$
2780
2781
\noindent where we have abbreviated $P(i, x, y)$ to $P$ for
2782
simplicity. The user defines the constants~$w_{\mathrm{exp}}$,
2783
$w_{\mathrm{sat}}$, $w_{\mathrm{cont}}$, and $w_{\mathrm{ent}}$ with
2784
the options `{\tt --exposure-weight}', `{\tt --saturation-weight}', `{\tt
2785
--contrast-weight}', and `{\tt --entropy-weight}' respectively. The
2786
functions~$f_{\mathrm{exp}}$, $f_{\mathrm{sat}}$, $f_{\mathrm{cont}}$,
2787
and $f_{\mathrm{ent}}$ along with the window sizes~$r_{\mathrm{cont}}$
2788
and $r_{\mathrm{ent}}$ are explained in the next sections.
2789
@end tex
2790
@docbook
2791
<informalequation>
2792
<mml:math>
2793
<mml:reln>
2794
<mml:eq/>
2795
<mml:apply>
2796
<mml:ci>w</mml:ci>
2797
<mml:ci>P</mml:ci>
2798
</mml:apply>
2799
<mml:apply>
2800
<mml:plus/>
2801
<mml:apply>
2802
<mml:times/>
2803
<mml:csymbol>
2804
<mml:msub>
2805
<mml:mi>w</mml:mi>
2806
<mml:mi mathvariant="normal">exp</mml:mi>
2807
</mml:msub>
2808
</mml:csymbol>
2809
<mml:apply>
2810
<mml:csymbol>
2811
<mml:msub>
2812
<mml:mi>f</mml:mi>
2813
<mml:mi mathvariant="normal">exp</mml:mi>
2814
</mml:msub>
2815
</mml:csymbol>
2816
<mml:ci>P</mml:ci>
2817
</mml:apply>
2818
</mml:apply>
2819
<mml:apply>
2820
<mml:times/>
2821
<mml:csymbol>
2822
<mml:msub>
2823
<mml:mi>w</mml:mi>
2824
<mml:mi mathvariant="normal">sat</mml:mi>
2825
</mml:msub>
2826
</mml:csymbol>
2827
<mml:apply>
2828
<mml:csymbol>
2829
<mml:msub>
2830
<mml:mi>f</mml:mi>
2831
<mml:mi mathvariant="normal">sat</mml:mi>
2832
</mml:msub>
2833
</mml:csymbol>
2834
<mml:ci>P</mml:ci>
2835
</mml:apply>
2836
</mml:apply>
2837
<mml:apply>
2838
<mml:times/>
2839
<mml:csymbol>
2840
<mml:msub>
2841
<mml:mi>w</mml:mi>
2842
<mml:mi mathvariant="normal">cont</mml:mi>
2843
</mml:msub>
2844
</mml:csymbol>
2845
<mml:apply>
2846
<mml:csymbol>
2847
<mml:msub>
2848
<mml:mi>f</mml:mi>
2849
<mml:mi mathvariant="normal">cont</mml:mi>
2850
</mml:msub>
2851
</mml:csymbol>
2852
<mml:ci>P</mml:ci>
2853
<mml:csymbol>
2854
<mml:msub>
2855
<mml:mi>r</mml:mi>
2856
<mml:mi mathvariant="normal">cont</mml:mi>
2857
</mml:msub>
2858
</mml:csymbol>
2859
</mml:apply>
2860
</mml:apply>
2861
2862
<mml:apply>
2863
<mml:times/>
2864
<mml:csymbol>
2865
<mml:msub>
2866
<mml:mi>w</mml:mi>
2867
<mml:mi mathvariant="normal">ent</mml:mi>
2868
</mml:msub>
2869
</mml:csymbol>
2870
<mml:apply>
2871
<mml:csymbol>
2872
<mml:msub>
2873
<mml:mi>f</mml:mi>
2874
<mml:mi mathvariant="normal">ent</mml:mi>
2875
</mml:msub>
2876
</mml:csymbol>
2877
<mml:ci>P</mml:ci>
2878
<mml:csymbol>
2879
<mml:msub>
2880
<mml:mi>r</mml:mi>
2881
<mml:mi mathvariant="normal">ent</mml:mi>
2882
</mml:msub>
2883
</mml:csymbol>
2884
</mml:apply>
2885
</mml:apply>
2886
2887
</mml:apply>
2888
</mml:reln>
2889
</mml:math>
2890
</informalequation>
2891
2892
where we have abbreviated <inlineequation> <mml:math> <mml:apply>
2893
<mml:ci>P</mml:ci> <mml:ci>i</mml:ci> <mml:ci>x</mml:ci>
2894
<mml:ci>y</mml:ci> </mml:apply> </mml:math> </inlineequation> to
2895
<inlineequation> <mml:math> <mml:ci>P</mml:ci> </mml:math>
2896
</inlineequation> for simplicity. The user defines the
2897
constants <inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2898
<mml:mi>w</mml:mi> <mml:mi mathvariant="normal">exp</mml:mi>
2899
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>,
2900
<inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2901
<mml:mi>w</mml:mi> <mml:mi mathvariant="normal">sat</mml:mi>
2902
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>,
2903
<inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2904
<mml:mi>w</mml:mi> <mml:mi mathvariant="normal">cont</mml:mi>
2905
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>, and
2906
<inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2907
<mml:mi>w</mml:mi> <mml:mi mathvariant="normal">ent</mml:mi>
2908
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>, with the
2909
options <literal>--exposure-weight</literal>,
2910
<literal>--saturation-weight</literal>,
2911
<literal>--contrast-weight</literal>, and
2912
<literal>--entropy-weight</literal> respectively. The
2913
functions <inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2914
<mml:mi>f</mml:mi> <mml:mi mathvariant="normal">exp</mml:mi>
2915
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>,
2916
<inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2917
<mml:mi>f</mml:mi> <mml:mi mathvariant="normal">sat</mml:mi>
2918
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>,
2919
<inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2920
<mml:mi>f</mml:mi> <mml:mi mathvariant="normal">cont</mml:mi>
2921
</mml:msub> </mml:csymbol> </mml:math> </inlineequation>, and
2922
<inlineequation> <mml:math> <mml:csymbol> <mml:msub>
2923
<mml:mi>f</mml:mi> <mml:mi mathvariant="normal">ent</mml:mi>
2924
</mml:msub> </mml:csymbol> </mml:math> </inlineequation> along with
2925
the window sizes <inlineequation> <mml:math> <mml:csymbol>
2926
<mml:msub> <mml:mi>r</mml:mi> <mml:mi
2927
mathvariant="normal">cont</mml:mi> </mml:msub>
2928
</mml:csymbol></mml:math> </inlineequation> and <inlineequation>
2929
<mml:math> <mml:csymbol> <mml:msub> <mml:mi>r</mml:mi> <mml:mi
2930
mathvariant="normal">ent</mml:mi> </mml:msub> </mml:csymbol>
2931
</mml:math> </inlineequation> are explained in the next sections.
2932
@end docbook
2933
2934
@menu
2935
* Weighted Average:: Enfuse's default weighting algorithm
2936
* Disabling Averaging:: ``Super Trouper'' weighting for focus stacks
2937
* Single Criterion Fusing:: Fusing with only one of the criteria
2938
@end menu
2939
2940
2941
@node Weighted Average
2942
@subsection Weighted Average
2943
@cindex weighted average
2944
@cindex average, weighted
2945
2946
By default, Enfuse uses a weighted average, where @emph{each} pixel
2947
contributes as much as its weight demands. Of course the weights can
2948
be extreme, favoring only a few pixels or even only one pixel in the
2949
input stack. Extremes are not typical, however.
2950
2951
Equal weights are another extreme that turns @equationW{} into an
2952
arithmetic average. This is why we sometimes speak of the ``averaging
2953
property'' of this weighting algorithm, like smoothing out noise.
2954
2955
2956
@node Disabling Averaging
2957
@subsection Disabling Averaging: Option@tie{}@option{--hard-mask}
2958
@cindex disabling average
2959
@cindex average, disabling
2960
@opindex --hard-mask
2961
2962
The weighted average computation as described above has proven to be
2963
widely successful with the exception of one special case: focus
2964
stacking (@pxref{Focus Stacks}), where the averaging noticeably
2965
softens the final image.
2966
2967
Use @option{--hard-mask} to switch Enfuse into a different (``Super
2968
Trouper'') weighting mode, where the pixel with the highest weight
2969
wins, this is, gets weight@tie{}one, and all other pixels get the
2970
weight of zero
2971
(@uref{http://@/en.wikipedia.org/@/wiki/@/The_@/Winner_@/Takes_@/It_@/All,,``The
2972
Winner Takes It All.''}). With @option{--hard-mask} Equation@tie{}@equationW{}
2973
becomes
2974
@ifinfo
2975
@display
2976
@math{P(i, x, y) --> Q(x, y),}
2977
@end display
2978
2979
@noindent
2980
where
2981
@display
2982
@math{w(P(i, x, y)) >= w(P(j, x, y))} for all @math{1 <= j <= n}.
2983
@end display
2984
@end ifinfo
2985
@html
2986
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
2987
<mrow>
2988
<mrow>
2989
<mrow>
2990
<mi>P</mi>
2991
<mfenced>
2992
<mi>i</mi>
2993
<mi>x</mi>
2994
<mi>y</mi>
2995
</mfenced>
2996
</mrow>
2997
<mo>→</mo>
2998
<mrow>
2999
<mi>Q</mi>
3000
<mfenced>
3001
<mi>x</mi>
3002
<mi>y</mi>
3003
</mfenced>
3004
</mrow>
3005
<mtext>,</mtext>
3006
</mrow>
3007
<mtext>  where  </mtext>
3008
<mrow>
3009
<mi>w</mi>
3010
<mo>⁡</mo>
3011
<mrow>
3012
<mo>(</mo>
3013
<mi>P</mi>
3014
<mfenced>
3015
<mi>i</mi>
3016
<mi>x</mi>
3017
<mi>y</mi>
3018
</mfenced>
3019
<mo>)</mo>
3020
</mrow>
3021
<mo>≥</mo>
3022
<mi>w</mi>
3023
<mo>⁡</mo>
3024
<mrow>
3025
<mo>(</mo>
3026
<mi>P</mi>
3027
<mfenced>
3028
<mi>j</mi>
3029
<mi>x</mi>
3030
<mi>y</mi>
3031
</mfenced>
3032
<mo>)</mo>
3033
</mrow>
3034
</mrow>
3035
<mtext>  for all  </mtext>
3036
<mrow>
3037
<mn>1</mn>
3038
<mo>≤</mo>
3039
<mi>j</mi>
3040
<mo>≤</mo>
3041
<mi>n</mi>
3042
</mrow>
3043
<mtext>.</mtext>
3044
</mrow>
3045
</math>
3046
@end html
3047
@tex
3048
$$
3049
P(i, x, y) \rightarrow Q(x, y),
3050
\hbox{ where } w(P(i, x, y)) \ge w(P(j, x, y))
3051
\hbox{ for all } 1 \le j \le n.
3052
$$
3053
@end tex
3054
@docbook
3055
<informalequation>
3056
<mml:math>
3057
<mml:lambda>
3058
<mml:bvar>
3059
<mml:apply>
3060
<mml:ci>P</mml:ci>
3061
<mml:ci>i</mml:ci>
3062
<mml:ci>x</mml:ci>
3063
<mml:ci>y</mml:ci>
3064
</mml:apply>
3065
</mml:bvar>
3066
<mml:apply>
3067
<mml:ci>Q</mml:ci>
3068
<mml:ci>x</mml:ci>
3069
<mml:ci>y</mml:ci>
3070
</mml:apply>
3071
</mml:lambda>
3072
</mml:math>
3073
</informalequation>
3074
where
3075
<informalequation>
3076
<mml:math>
3077
<mml:apply>
3078
<mml:forall/>
3079
<mml:bvar>
3080
<mml:condition>
3081
<mml:reln>
3082
<mml:leq/>
3083
<mml:cn>1</mml:cn>
3084
<mml:ci>j</mml:ci>
3085
<mml:ci>n</mml:ci>
3086
</mml:reln>
3087
</mml:condition>
3088
</mml:bvar>
3089
<mml:reln>
3090
<mml:geq/>
3091
<mml:apply>
3092
<mml:ci>w</mml:ci>
3093
<mml:apply>
3094
<mml:ci>P</mml:ci>
3095
<mml:ci>i</mml:ci>
3096
<mml:ci>x</mml:ci>
3097
<mml:ci>y</mml:ci>
3098
</mml:apply>
3099
</mml:apply>
3100
<mml:apply>
3101
<mml:ci>w</mml:ci>
3102
<mml:apply>
3103
<mml:ci>P</mml:ci>
3104
<mml:ci>j</mml:ci>
3105
<mml:ci>x</mml:ci>
3106
<mml:ci>y</mml:ci>
3107
</mml:apply>
3108
</mml:apply>
3109
</mml:reln>
3110
</mml:apply>
3111
</mml:math>
3112
</informalequation>
3113
@end docbook
3114
3115
@noindent
3116
Note that this ``averaging'' scheme lacks the nice noise-reduction
3117
property of the weighted average@tie{}@equationW{}, because only a
3118
single input pixel contributes to the output.
3119
3120
3121
@node Single Criterion Fusing
3122
@subsection Single Criterion Fusing
3123
@cindex single criterion fusing
3124
@cindex fusing, single criterion
3125
3126
Enfuse allows the user to weight each pixel of an input image by up to
3127
four different criteria (@pxref{Overview}). However, it does not
3128
force the user to do so. For some applications and more often simply
3129
to gain further insight into the weighting and fusing process, looking
3130
at only a single criterion is the preferred way to work.
3131
3132
@cindex active criterion
3133
@cindex criterion, active
3134
The version of Enfuse for which this documentation was prepared, uses
3135
the default weights as stated in @ref{Table:default-weights}. Notice
3136
that by default @emph{more than one} weight is larger than zero, which
3137
means they are @emph{active}.
3138
3139
@float Table,Table:default-weights
3140
@multitable {Local Contrast} {0.0}
3141
@headitem Criterion @tab Weight
3142
@item Exposure @tab @value{src::default-weight-exposure}
3143
@item Saturation @tab @value{src::default-weight-saturation}
3144
@item Local Contrast @tab @value{src::default-weight-contrast}
3145
@item Local Entropy @tab @value{src::default-weight-entropy}
3146
@end multitable
3147
3148
@caption{Enfuse's default weights as compiled into version@tie{}@value{VERSION}.}
3149
3150
@shortcaption{Default weights}
3151
3152
@cindex default weights
3153
@cindex weights, default
3154
@end float
3155
3156
To disable a particular criterion set its weight to zero as for
3157
example
3158
@example
3159
enfuse \
3160
--exposure-weight=1 --saturation-weight=0 \
3161
--contrast-weight=0 --entropy-weight=0 \
3162
img_[1-3].png
3163
@end example
3164
instructs Enfuse to consider only the exposure weight. Combine this
3165
with option@tie{}@option{--save-masks} and it will become clearer how
3166
Enfuse computes the exposure weight for the set of images.
3167
3168
@cindex overpowering criteria
3169
@cindex criteria, overpowering one another
3170
Another problem that can be inspected by fusing with just a single
3171
active criterion and saving the masks is if the weights of one
3172
criterion completely overpower all others.
3173
3174
3175
@node Exposure Weighting
3176
@section Exposure Weighting
3177
@cindex weighting, exposure
3178
3179
Exposure weighting prefers pixels with a luminance@tie{}@math{Y} close
3180
to the center of the normalized, real-valued luminance
3181
interval@tie{}@math{[0, 1]}.
3182
3183
@acronym{RGB}-pixels get converted to luminance using the grayscale
3184
projector given by @option{--gray-@/projector}, which defaults to
3185
@code{average}. Grayscale pixels are identified with luminance.
3186
3187
In the normalized luminance interval 0.0 represents pure black and 1.0
3188
represents pure white independently of the data type of the input
3189
image. This is, for a @acronym{JPEG} image the luminance@tie{}255
3190
maps to 1.0 in the normalized interval and for a 32@dmn{bit}
3191
@acronym{TIFF} picture the highest luminance value@tie{}4294967295
3192
also maps to 1.0. The middle of the luminance interval, 0.5, is where
3193
a neutral gray tone ends up with every camera that had no exposure
3194
correction dialed in, for example the image of a gray- or white-card.
3195
3196
The exposure weighting algorithm only looks at a single pixel at a
3197
time; the pixel's neighborhood is not taken into account.
3198
3199
The weighting function is the Gaussian
3200
@ifinfo
3201
@display
3202
@math{w_exp(Y) = exp(-0.5 * ((Y - Mu) / Sigma)^2),}
3203
@end display
3204
@end ifinfo
3205
@html
3206
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3207
<mrow>
3208
<mrow>
3209
<msub>
3210
<mi>w</mi>
3211
<mtext>exp</mtext>
3212
</msub>
3213
<mo>⁡</mo>
3214
<mrow>
3215
<mo>(</mo>
3216
<mi>Y</mi>
3217
<mo>)</mo>
3218
</mrow>
3219
</mrow>
3220
<mo>=</mo>
3221
<mrow>
3222
<mtext>exp</mtext>
3223
<mo>⁡</mo>
3224
<mrow>
3225
<mo>(</mo>
3226
<mo>-</mo>
3227
<mfrac>
3228
<mn>1</mn>
3229
<mn>2</mn>
3230
</mfrac>
3231
<mo>⁢</mo>
3232
<msup>
3233
<mrow>
3234
<mo>(</mo>
3235
<mfrac>
3236
<mrow>
3237
<mi>Y</mi>
3238
<mo>-</mo>
3239
<mi mathvariant="italic">Mu</mi>
3240
</mrow>
3241
<mi mathvariant="italic">Sigma</mi>
3242
</mfrac>
3243
<mo>)</mo>
3244
</mrow>
3245
<mn>2</mn>
3246
</msup>
3247
<mo>)</mo>
3248
</mrow>
3249
</mrow>
3250
</mrow>
3251
</math>
3252
@end html
3253
@tex
3254
$$
3255
w_{\mathrm{exp}}(Y) =
3256
\exp\left(-{1 \over 2}
3257
\left(Y - \mathit{Mu} \over \mathit{Sigma} \right)^2\right),
3258
$$
3259
@end tex
3260
@docbook
3261
<informalequation>
3262
<mml:math>
3263
<mml:reln>
3264
<mml:eq/>
3265
<mml:apply>
3266
<mml:csymbol>
3267
<mml:msub>
3268
<mml:mi>w</mml:mi>
3269
<mml:mi mathvariant="normal">exp</mml:mi>
3270
</mml:msub>
3271
</mml:csymbol>
3272
<mml:ci>Y</mml:ci>
3273
</mml:apply>
3274
<mml:apply>
3275
<mml:exp/>
3276
<mml:apply>
3277
<mml:times/>
3278
<mml:apply>
3279
<mml:minus/>
3280
<mml:apply>
3281
<mml:divide/>
3282
<mml:cn>1</mml:cn>
3283
<mml:cn>2</mml:cn>
3284
</mml:apply>
3285
</mml:apply>
3286
<mml:apply>
3287
<mml:power/>
3288
<mml:apply>
3289
<mml:divide/>
3290
<mml:apply>
3291
<mml:minus/>
3292
<mml:ci>Y</mml:ci>
3293
<mml:ci>Mu</mml:ci>
3294
</mml:apply>
3295
<mml:ci>Sigma</mml:ci>
3296
</mml:apply>
3297
<mml:cn>2</mml:cn>
3298
</mml:apply>
3299
</mml:apply>
3300
</mml:apply>
3301
</mml:reln>
3302
</mml:math>
3303
</informalequation>
3304
@end docbook
3305
3306
@noindent
3307
whose center@tie{}@math{Mu} and width@tie{}@math{Sigma} are controlled
3308
by the command line options@tie{}@option{--exposure-mu} and @option{--exposure-sigma}
3309
respectively. @math{Mu} defaults to @value{src::default-exposure-mu}
3310
and @math{Sigma} defaults to @value{src::default-exposure-sigma}.
3311
@ref{Figure:gaussian} shows a Gaussian.
3312
3313
@float Figure,Figure:gaussian
3314
@vimage{gaussian}
3315
3316
@caption{Gaussian function with the parameters @var{Mu} = 0.5 and @var{Sigma} = 0.2.}
3317
3318
@shortcaption{Gaussian function}
3319
@end float
3320
3321
The options@tie{}@option{--exposure-mu} and @option{--exposure-sigma} are for
3322
fine-tuning the final result without changing the set of input images.
3323
Option@tie{}@option{--exposure-mu} sets the point @var{Mu} of optimum
3324
exposure. Increasing @var{Mu} makes Enfuse prefer lighter pixels,
3325
rendering the final image lighter, and vice versa.
3326
Option@tie{}@option{--exposure-sigma} defines the range @var{Sigma} of
3327
acceptable exposures. Small values of @var{Sigma} penalize exposures
3328
that deviate from @var{Mu} more, and vice versa.
3329
3330
@optionsummaryheading{}
3331
3332
@table @option
3333
@item --exposure-weight
3334
@ref{Fusion Options}
3335
3336
@item --exposure-mu
3337
@ref{Fusion Options}
3338
3339
@item --exposure-sigma
3340
@ref{Fusion Options}
3341
3342
@item --gray-projector
3343
@ref{Expert Options}
3344
@end table
3345
3346
3347
@node Saturation Weighting
3348
@section Saturation Weighting
3349
@cindex weighting, saturation
3350
3351
Saturation weighting prefers pixels with a high saturation.
3352
3353
Enfuse computes the saturation of a pixel according to the following
3354
algorithm.
3355
3356
@example
3357
@group
3358
@var{max} := maximum(@var{R}, @var{G}, @var{B})
3359
@var{min} := minimum(@var{R}, @var{G}, @var{B})
3360
@b{if} @var{max} = @var{min} @b{then}
3361
@var{saturation} := 0
3362
@b{else}
3363
@var{sum} := @var{max} + @var{min}
3364
@var{difference} := @var{max} - @var{min}
3365
@b{if} @var{sum} @leq{} 1 @b{then}
3366
@var{saturation} := @var{difference} / @var{sum}
3367
@b{else}
3368
@var{saturation} := @var{difference} / (2 - @var{sum})
3369
@b{end if}
3370
@b{end if}
3371
@end group
3372
@end example
3373
3374
@noindent
3375
Obviously, saturation weighting can only be defined for @acronym{RGB}
3376
images, not for grayscale ones! If you need something similar, check
3377
out @ref{Local Entropy Weighting}; entropy weighting works for both
3378
@acronym{RGB} and grayscale pictures.
3379
3380
The saturation weighting algorithm only looks at a single pixel at a
3381
time; the pixel's neighborhood is not taken into account.
3382
3383
@optionsummaryheading{}
3384
3385
@table @option
3386
@item --saturation-weight
3387
@ref{Fusion Options}
3388
@end table
3389
3390
3391
@node Local Contrast Weighting
3392
@section Local Contrast Weighting
3393
@cindex weighting, local contrast
3394
3395
Local contrast weighting favors pixels inside a high contrast
3396
neighborhood. The notion of ``high contrast'' is defined either by
3397
two different criteria or by a blend of both:
3398
3399
@itemize
3400
@item
3401
The standard deviation (@acronym{SDev}) of all the pixels in the local
3402
analysis window is large. @xref{Standard Deviation}.
3403
3404
@item
3405
The Laplacian-of-Gaussian (@acronym{LoG}) has a large magnitude.
3406
@xref{Laplacian of Gaussian}.
3407
3408
@item
3409
If the @acronym{LoG} magnitude is below a given threshold, use
3410
@acronym{SDev} data, otherwise stick with @acronym{LoG}.
3411
@xref{Blend SDev and LoG}.
3412
@end itemize
3413
3414
Enfuse converts every @acronym{RGB} image to grayscale before it
3415
determines its contrast. Option@tie{}@option{--gray-projector}
3416
(@pxref{Expert Options}) controls the projector function. Depending
3417
on the subject, one of several grayscale projectors may yield the best
3418
black-and-white contrast for image fusion.
3419
3420
In the following sections we describe each algorithm in detail.
3421
3422
@menu
3423
* Standard Deviation:: Standard deviation (@acronym{SDev})
3424
* Laplacian of Gaussian:: @acronym{LoG}, a second derivative method
3425
* Blend SDev and LoG:: Mix and match @acronym{SDev} and @acronym{LoG}
3426
* Scaling and Choice of Mode:: How parameters do not scale; neither does mode
3427
@end menu
3428
3429
3430
@node Standard Deviation
3431
@subsection Standard Deviation
3432
@cindex weighting, contrast using standard deviation
3433
@cindex contrast weighting using standard deviation
3434
3435
@cindex local analysis window
3436
@cindex window, local-analysis
3437
The pixel under consideration@tie{}C sits exactly in the center of a
3438
square, the so-called @dfn{local analysis window}. It always has an
3439
uneven edge length. The user sets the size with
3440
option@tie{}@option{--contrast-window-size}.
3441
@ref{Figure:local-analysis-window} shows two windows with different
3442
sizes.
3443
3444
@float Figure,Figure:local-analysis-window
3445
@vimage{local-analysis-window}
3446
3447
@caption{Examples of local analysis windows for the sizes 3 and 5. ``C'' marks the center where the pixel gets the weight. ``N'' are neighboring pixels, which all contribute equally to the weight.}
3448
3449
@shortcaption{Local analysis window}
3450
@end float
3451
3452
During the analysis, Enfuse scans the local analysis window across all
3453
rows and all columns@footnote{In the current implementation a
3454
@code{floor(contrast-window-size / 2)} wide border around the images
3455
remains unprocessed and gets a weight of zero.} of each of the input
3456
images to compute the contrast weight of every pixel.
3457
3458
@optionsummaryheading{}
3459
3460
@table @option
3461
@item --contrast-weight
3462
@ref{Fusion Options}
3463
3464
@item --hard-mask
3465
@ref{Fusion Options}
3466
3467
@item --contrast-window-size
3468
@ref{Expert Options}
3469
3470
@item --gray-projector
3471
@ref{Expert Options}
3472
@end table
3473
3474
3475
@subsubsection Statistical Moments
3476
@cindex statistical moments
3477
3478
@cindex probability function
3479
We start with the @dfn{probability function} @math{w} of the random
3480
variable@tie{}@math{X}:
3481
@ifinfo
3482
@display
3483
@math{w: x --> p(@{omega: X(omega) = x@})}.
3484
@end display
3485
@end ifinfo
3486
@html
3487
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3488
<mrow>
3489
<mi>w</mi>
3490
<mo>:</mo>
3491
<mrow>
3492
<mi>x</mi>
3493
<mo>→</mo>
3494
<mi>p</mi>
3495
<mo>⁡</mo>
3496
<mo>(</mo>
3497
<mrow>
3498
<mo>{</mo>
3499
<mrow>
3500
<mi>ω</mi>
3501
<mo>:</mo>
3502
<mrow>
3503
<mi>X</mi>
3504
<mo>⁡</mo>
3505
<mrow>
3506
<mo>(</mo>
3507
<mi>ω</mi>
3508
<mo>)</mo>
3509
</mrow>
3510
<mo>=</mo>
3511
<mi>x</mi>
3512
</mrow>
3513
</mrow>
3514
<mo>}</mo>
3515
</mrow>
3516
<mo>)</mo>
3517
</mrow>
3518
<mtext>.</mtext>
3519
</mrow>
3520
</math>
3521
@end html
3522
@tex
3523
$$
3524
w: x \rightarrow p(\{\omega: X(\omega) = x\}).
3525
$$
3526
@end tex
3527
@docbook
3528
<informalequation>
3529
<mml:math>
3530
<mml:apply>
3531
<mml:csymbol>
3532
<mml:mo>:</mml:mo>
3533
</mml:csymbol>
3534
<mml:ci>w</mml:ci>
3535
<mml:lambda>
3536
<mml:bvar>
3537
<mml:ci>x</mml:ci>
3538
</mml:bvar>
3539
<mml:apply>
3540
<mml:ci>p</mml:ci>
3541
<mml:set>
3542
<mml:bvar>
3543
<mml:ci>ω</mml:ci>
3544
</mml:bvar>
3545
<mml:condition>
3546
<mml:reln>
3547
<mml:eq/>
3548
<mml:apply>
3549
<mml:ci>X</mml:ci>
3550
<mml:ci>ω</mml:ci>
3551
</mml:apply>
3552
<mml:ci>x</mml:ci>
3553
</mml:reln>
3554
</mml:condition>
3555
</mml:set>
3556
</mml:apply>
3557
</mml:lambda>
3558
</mml:apply>
3559
</mml:math>
3560
</informalequation>
3561
@end docbook
3562
3563
@noindent
3564
It associates a probability@tie{}@math{p} with each of the @math{n}
3565
different possible outcomes@tie{}@inlineomega{} of the random
3566
variable@tie{}@math{X}.
3567
@cindex expectation value
3568
Based on @math{w}, we define the @dfn{expectation value} or ``First
3569
Moment'' of the random variable@tie{}@math{X}:
3570
@ifinfo
3571
@display
3572
@math{Ex X := sum(x_i * w(x_i), i = 1..n).}
3573
@end display
3574
@end ifinfo
3575
@html
3576
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3577
<mrow>
3578
<mrow>
3579
<mo mathvariant="sans-serif">Ex</mo>
3580
<mo>⁡</mo>
3581
<mi>X</mi>
3582
</mrow>
3583
<mo>:=</mo>
3584
<mrow>
3585
<munderover>
3586
<mo>∑</mo>
3587
<mrow>
3588
<mi>i</mi>
3589
<mo>=</mo>
3590
<mn>1</mn>
3591
</mrow>
3592
<mi>n</mi>
3593
</munderover>
3594
<msub>
3595
<mi>x</mi>
3596
<mi>i</mi>
3597
</msub>
3598
<mo>×</mo>
3599
<mi>w</mi>
3600
<mo>⁡</mo>
3601
<mrow>
3602
<mo>(</mo>
3603
<msub>
3604
<mi>x</mi>
3605
<mi>i</mi>
3606
</msub>
3607
<mo>)</mo>
3608
</mrow>
3609
<mtext>.</mtext>
3610
</mrow>
3611
</mrow>
3612
</math>
3613
@end html
3614
@tex
3615
$$
3616
\hbox{\sf Ex } X := \sum_{i = 1}^n x_i w(x_i).
3617
$$
3618
@end tex
3619
@docbook
3620
<informalequation>
3621
<mml:math>
3622
<mml:reln>
3623
<mml:eq/>
3624
<mml:apply>
3625
<mml:csymbol>
3626
<mml:mtext mathvariant="sans-serif">Ex</mml:mtext>
3627
</mml:csymbol>
3628
<mml:ci>X</mml:ci>
3629
</mml:apply>
3630
<mml:apply>
3631
<mml:moment/>
3632
<mml:degree>
3633
<mml:cn>1</mml:cn>
3634
</mml:degree>
3635
<mml:ci>X</mml:ci>
3636
</mml:apply>
3637
<mml:apply>
3638
<mml:sum/>
3639
<mml:bvar>
3640
<mml:ci>i</mml:ci>
3641
</mml:bvar>
3642
<mml:lowlimit>
3643
<mml:cn>1</mml:cn>
3644
</mml:lowlimit>
3645
<mml:uplimit>
3646
<mml:ci>n</mml:ci>
3647
</mml:uplimit>
3648
<mml:apply>
3649
<mml:times/>
3650
<mml:apply>
3651
<mml:selector/>
3652
<mml:ci>x</mml:ci>
3653
<mml:ci>i</mml:ci>
3654
</mml:apply>
3655
<mml:apply>
3656
<mml:ci>w</mml:ci>
3657
<mml:apply>
3658
<mml:selector/>
3659
<mml:ci>x</mml:ci>
3660
<mml:ci>i</mml:ci>
3661
</mml:apply>
3662
</mml:apply>
3663
</mml:apply>
3664
</mml:apply>
3665
</mml:reln>
3666
</mml:math>
3667
</informalequation>
3668
@end docbook
3669
3670
@cindex variance
3671
@noindent
3672
Using the definition of the expectation value, we define the
3673
@dfn{variance}, or ``Second Moment'' as
3674
@ifinfo
3675
@display
3676
@math{Var X := Ex((X - Ex X)^2)},
3677
@end display
3678
@end ifinfo
3679
@html
3680
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3681
<mrow>
3682
<mo mathvariant="sans-serif">Var</mo>
3683
<mo>⁡</mo>
3684
<mi>X</mi>
3685
</mrow>
3686
<mo>:=</mo>
3687
<mrow>
3688
<mo mathvariant="sans-serif">Ex</mo>
3689
<mo>⁡</mo>
3690
<mrow>
3691
<mo>(</mo>
3692
<msup>
3693
<mrow>
3694
<mo>(</mo>
3695
<mi>X</mi>
3696
<mo>-</mo>
3697
<mrow>
3698
<mo mathvariant="sans-serif">Ex</mo>
3699
<mo>⁡</mo>
3700
<mi>X</mi>
3701
</mrow>
3702
<mo>)</mo>
3703
</mrow>
3704
<mn>2</mn>
3705
</msup>
3706
<mo>)</mo>
3707
</mrow>
3708
</mrow>
3709
</math>
3710
@end html
3711
@tex
3712
$$
3713
\hbox{\sf Var } X := \hbox{\sf Ex}\left( (X - \hbox{\sf Ex } X)^2 \right),
3714
$$
3715
@end tex
3716
@docbook
3717
<informalequation>
3718
<mml:math>
3719
<mml:reln>
3720
<mml:eq/>
3721
<mml:apply>
3722
<mml:csymbol>
3723
<mml:mtext mathvariant="sans-serif">Var</mml:mtext>
3724
</mml:csymbol>
3725
<mml:ci>X</mml:ci>
3726
</mml:apply>
3727
<mml:apply>
3728
<mml:variance/>
3729
<mml:ci>X</mml:ci>
3730
</mml:apply>
3731
<mml:apply>
3732
<mml:moment/>
3733
<mml:degree>
3734
<mml:cn>2</mml:cn>
3735
</mml:degree>
3736
<mml:ci>X</mml:ci>
3737
</mml:apply>
3738
<mml:apply>
3739
<mml:csymbol>
3740
<mml:mtext mathvariant="sans-serif">Ex</mml:mtext>
3741
</mml:csymbol>
3742
<mml:apply>
3743
<mml:power/>
3744
<mml:apply>
3745
<mml:minus/>
3746
<mml:ci>X</mml:ci>
3747
<mml:apply>
3748
<mml:csymbol>
3749
<mml:mtext mathvariant="sans-serif">Ex</mml:mtext>
3750
</mml:csymbol>
3751
<mml:ci>X</mml:ci>
3752
</mml:apply>
3753
</mml:apply>
3754
<mml:cn>2</mml:cn>
3755
</mml:apply>
3756
</mml:apply>
3757
</mml:reln>
3758
</mml:math>
3759
</informalequation>
3760
@end docbook
3761
3762
@cindex standard deviation
3763
@noindent
3764
and the @dfn{standard deviation} as
3765
@ifinfo
3766
@display
3767
@math{Sdev X := sqrt(Var X)}.
3768
@end display
3769
@end ifinfo
3770
@html
3771
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3772
<mrow>
3773
<mrow>
3774
<mo>σ</mo>
3775
<mo>⁡</mo>
3776
<mi>X</mi>
3777
</mrow>
3778
<mo>:=</mo>
3779
<msqrt>
3780
<mo mathvariant="sans-serif">Var</mo>
3781
<mo>⁡</mo>
3782
<mi>X</mi>
3783
</msqrt>
3784
<mtext>.</mtext>
3785
</mrow>
3786
</math>
3787
@end html
3788
@tex
3789
$$
3790
\sigma X := \sqrt{\hbox{\sf Var } X}.
3791
$$
3792
@end tex
3793
@docbook
3794
<informalequation>
3795
<mml:math>
3796
<mml:reln>
3797
<mml:eq/>
3798
<mml:apply>
3799
<mml:sdev/>
3800
<mml:ci>X</mml:ci>
3801
</mml:apply>
3802
<mml:apply>
3803
<mml:root/>
3804
<mml:degree>
3805
<mml:cn>2</mml:cn>
3806
</mml:degree>
3807
<mml:apply>
3808
<mml:moment/>
3809
<mml:degree>
3810
<mml:cn>2</mml:cn>
3811
</mml:degree>
3812
<mml:ci>X</mml:ci>
3813
</mml:apply>
3814
</mml:apply>
3815
<mml:apply>
3816
<mml:root/>
3817
<mml:degree>
3818
<mml:cn>2</mml:cn>
3819
</mml:degree>
3820
<mml:apply>
3821
<mml:csymbol>
3822
<mml:mtext mathvariant="sans-serif">Var</mml:mtext>
3823
</mml:csymbol>
3824
<mml:ci>X</mml:ci>
3825
</mml:apply>
3826
</mml:apply>
3827
</mml:reln>
3828
</mml:math>
3829
</informalequation>
3830
@end docbook
3831
3832
Obviously, the variance of @math{X} is the expectation value of the
3833
squared deviation from the expectation value of @math{X} itself. Note
3834
that the variance's dimension is @math{X}'s dimension squared; the
3835
standard deviation rectifies the dimension to make it comparable with
3836
@math{X} itself again.
3837
3838
3839
@subsubsection Estimators
3840
@cindex estimators
3841
3842
In Enfuse, we assume that @math{X} follows a uniform probability
3843
function@tie{}@math{w(x)} = const. That is, all pixel values in the
3844
local analysis window are considered to be equally probable. Thus,
3845
the expectation value and the variance can be estimated from the pixel
3846
values like this
3847
@ifinfo
3848
@display
3849
@math{Ex X = sum(x_i, i = 1..n) / n.}
3850
@end display
3851
@end ifinfo
3852
@html
3853
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3854
<mrow>
3855
<mrow>
3856
<mo mathvariant="sans-serif">Ex</mo>
3857
<mo>⁡</mo>
3858
<mi>X</mi>
3859
</mrow>
3860
<mo>:=</mo>
3861
<mrow>
3862
<mfrac>
3863
<mn>1</mn>
3864
<mi>n</mi>
3865
</mfrac>
3866
<mo>⁢</mo>
3867
<mrow>
3868
<munderover>
3869
<mo>∑</mo>
3870
<mrow>
3871
<mi>i</mi>
3872
<mo>=</mo>
3873
<mn>1</mn>
3874
</mrow>
3875
<mi>n</mi>
3876
</munderover>
3877
<msub>
3878
<mi>x</mi>
3879
<mi>i</mi>
3880
</msub>
3881
</mrow>
3882
</mrow>
3883
<mtext>.</mtext>
3884
</mrow>
3885
</math>
3886
@end html
3887
@tex
3888
$$
3889
\hbox{\sf Ex } X := {1 \over n} \sum_{i = 1}^n x_i.
3890
$$
3891
@end tex
3892
@docbook
3893
<informalequation>
3894
<mml:math>
3895
<mml:reln>
3896
<mml:eq/>
3897
<mml:apply>
3898
<mml:csymbol>
3899
<mml:mtext mathvariant="sans-serif">Ex</mml:mtext>
3900
</mml:csymbol>
3901
<mml:ci>X</mml:ci>
3902
</mml:apply>
3903
<mml:apply>
3904
<mml:times/>
3905
<mml:apply>
3906
<mml:divide/>
3907
<mml:cn>1</mml:cn>
3908
<mml:ci>n</mml:ci>
3909
</mml:apply>
3910
<mml:apply>
3911
<mml:sum/>
3912
<mml:bvar>
3913
<mml:ci>i</mml:ci>
3914
</mml:bvar>
3915
<mml:lowlimit>
3916
<mml:cn>1</mml:cn>
3917
</mml:lowlimit>
3918
<mml:uplimit>
3919
<mml:ci>n</mml:ci>
3920
</mml:uplimit>
3921
<mml:apply>
3922
<mml:selector/>
3923
<mml:ci>x</mml:ci>
3924
<mml:ci>i</mml:ci>
3925
</mml:apply>
3926
</mml:apply>
3927
</mml:apply>
3928
</mml:reln>
3929
</mml:math>
3930
</informalequation>
3931
@end docbook
3932
3933
@noindent
3934
In other words: the expectation value is the arithmetic mean of the
3935
lightness of all pixels in the local analysis window. Analogously,
3936
the variance becomes
3937
@ifinfo
3938
@display
3939
@math{Var X = sum((x_i - Ex x)^2, i = 1..n) / (n - 1).}
3940
@end display
3941
@end ifinfo
3942
@html
3943
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
3944
<mrow>
3945
<mrow>
3946
<mo mathvariant="sans-serif">Var</mo>
3947
<mo>⁡</mo>
3948
<mi>X</mi>
3949
</mrow>
3950
<mo>:=</mo>
3951
<mfrac>
3952
<mn>1</mn>
3953
<mrow>
3954
<mi>n</mi>
3955
<mo>-</mo>
3956
<mn>1</mn>
3957
</mrow>
3958
</mfrac>
3959
<mo>⁢</mo>
3960
<mrow>
3961
<mo mathvariant="sans-serif">Ex</mo>
3962
<mo>⁡</mo>
3963
<mrow>
3964
<mo>(</mo>
3965
<msup>
3966
<mrow>
3967
<mo>(</mo>
3968
<mi>X</mi>
3969
<mo>-</mo>
3970
<mrow>
3971
<mo mathvariant="sans-serif">Ex</mo>
3972
<mo>⁡</mo>
3973
<mi>X</mi>
3974
</mrow>
3975
<mo>)</mo>
3976
</mrow>
3977
<mn>2</mn>
3978
</msup>
3979
<mo>)</mo>
3980
</mrow>
3981
</mrow>
3982
<mtext>.</mtext>
3983
</mrow>
3984
</math>
3985
@end html
3986
@tex
3987
$$
3988
\hbox{\sf Var } X :=
3989
{1 \over {n - 1}} \, \hbox{\sf Ex}\left( (X - \hbox{\sf Ex } X)^2 \right).
3990
$$
3991
@end tex
3992
@docbook
3993
<informalequation>
3994
<mml:math>
3995
<mml:reln>
3996
<mml:eq/>
3997
<mml:apply>
3998
<mml:csymbol>
3999
<mml:mtext mathvariant="sans-serif">Var</mml:mtext>
4000
</mml:csymbol>
4001
<mml:ci>X</mml:ci>
4002
</mml:apply>
4003
<mml:apply>
4004
<mml:times/>
4005
<mml:apply>
4006
<mml:divide/>
4007
<mml:cn>1</mml:cn>
4008
<mml:apply>
4009
<mml:minus/>
4010
<mml:ci>n</mml:ci>
4011
<mml:cn>1</mml:cn>
4012
</mml:apply>
4013
</mml:apply>
4014
<mml:apply>
4015
<mml:csymbol>
4016
<mml:mtext mathvariant="sans-serif">Ex</mml:mtext>
4017
</mml:csymbol>
4018
<mml:apply>
4019
<mml:power/>
4020
<mml:apply>
4021
<mml:minus/>
4022
<mml:ci>X</mml:ci>
4023
<mml:apply>
4024
<mml:csymbol>
4025
<mml:mtext mathvariant="sans-serif">Ex</mml:mtext>
4026
</mml:csymbol>
4027
<mml:ci>X</mml:ci>
4028
</mml:apply>
4029
</mml:apply>
4030
<mml:cn>2</mml:cn>
4031
</mml:apply>
4032
</mml:apply>
4033
</mml:apply>
4034
</mml:reln>
4035
</mml:math>
4036
</informalequation>
4037
@end docbook
4038
4039
4040
@node Laplacian of Gaussian
4041
@subsection Laplacian of Gaussian
4042
@cindex weighting, contrast using laplacian-of--gaussian
4043
@cindex contrast weighting using laplacian-of--gaussian
4044
4045
@cindex Laplacian of Gaussian (@acronym{LoG})
4046
The @dfn{Laplacian of Gaussian} (@acronym{LoG}) is an operator to
4047
detect edges in an image. Sometimes the @acronym{LoG}-operator is
4048
also called @sc{Marr}-@sc{Hildreth} operator. A Laplacian-of-Gaussian
4049
operator,
4050
@uref{http://@/hci.iwr.uni-@/heidelberg.de/@/vigra/@/doc/@/vigra/@/group__@/Common@/Convolution@/Filters.html,
4051
@code{vigra::@/laplacian@/Of@/Gaussian}} is part of the
4052
package@tie{}@uref{http://@/hci.iwr.uni-@/heidelberg.de/@/vigra/,
4053
@acronym{VIGRA}} that Enfuse is built upon and is used for edge
4054
detection if option@tie{}@option{--contrast-edge-scale} is non-zero and
4055
@option{--contrast-min-curvature} equal to or less than zero.
4056
4057
Let the Gaussian function be
4058
@ifinfo
4059
@display
4060
@math{g(x, y) = 1/pi * exp((x^2 + y^2) / (2 * sigma^2))/(2 * sigma^2)}
4061
@end display
4062
@end ifinfo
4063
@html
4064
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4065
<mrow>
4066
<mrow>
4067
<mi>g</mi>
4068
<mfenced>
4069
<mi>x</mi>
4070
<mi>y</mi>
4071
</mfenced>
4072
</mrow>
4073
<mo>=</mo>
4074
<mrow>
4075
<mfrac>
4076
<mn>1</mn>
4077
<mrow>
4078
<mn>2</mn>
4079
<mo>⁢</mo>
4080
<mi>π</mi>
4081
<mo>⁢</mo>
4082
<msup>
4083
<mi>σ</mi>
4084
<mn>2</mn>
4085
</msup>
4086
</mrow>
4087
</mfrac>
4088
<mo>⁢</mo>
4089
<mtext>exp</mtext>
4090
<mo>⁡</mo>
4091
<mrow>
4092
<mo>(</mo>
4093
<mo>-</mo>
4094
<mfrac>
4095
<mrow>
4096
<msup>
4097
<mi>x</mi>
4098
<mn>2</mn>
4099
</msup>
4100
<mo>+</mo>
4101
<msup>
4102
<mi>y</mi>
4103
<mn>2</mn>
4104
</msup>
4105
</mrow>
4106
<mrow>
4107
<mn>2</mn>
4108
<mo>⁢</mo>
4109
<msup>
4110
<mi>σ</mi>
4111
<mn>2</mn>
4112
</msup>
4113
</mrow>
4114
</mfrac>
4115
<mo>)</mo>
4116
</mrow>
4117
</mrow>
4118
</mrow>
4119
</math>
4120
@end html
4121
@tex
4122
$$
4123
g(x, y) =
4124
{1 \over {2 \pi \sigma^2}} \,
4125
{\exp\left(-{{x^2 + y^2} \over {2 \sigma^2}}\right)}
4126
$$
4127
@end tex
4128
@docbook
4129
<informalequation>
4130
<mml:math>
4131
<mml:reln>
4132
<mml:eq/>
4133
<mml:apply>
4134
<mml:ci>g</mml:ci>
4135
<mml:ci>x</mml:ci>
4136
<mml:ci>y</mml:ci>
4137
</mml:apply>
4138
<mml:apply>
4139
<mml:times/>
4140
<mml:apply>
4141
<mml:divide/>
4142
<mml:cn>1</mml:cn>
4143
<mml:apply>
4144
<mml:times/>
4145
<mml:cn>2</mml:cn>
4146
<mml:csymbol>π</mml:csymbol>
4147
<mml:apply>
4148
<mml:power/>
4149
<mml:ci>σ</mml:ci>
4150
<mml:cn>2</mml:cn>
4151
</mml:apply>
4152
</mml:apply>
4153
</mml:apply>
4154
<mml:apply>
4155
<mml:exp/>
4156
<mml:apply>
4157
<mml:minus/>
4158
<mml:apply>
4159
<mml:divide/>
4160
<mml:apply>
4161
<mml:plus/>
4162
<mml:apply>
4163
<mml:power/>
4164
<mml:ci>x</mml:ci>
4165
<mml:cn>2</mml:cn>
4166
</mml:apply>
4167
<mml:apply>
4168
<mml:power/>
4169
<mml:ci>y</mml:ci>
4170
<mml:cn>2</mml:cn>
4171
</mml:apply>
4172
</mml:apply>
4173
<mml:apply>
4174
<mml:times/>
4175
<mml:cn>2</mml:cn>
4176
<mml:apply>
4177
<mml:power/>
4178
<mml:ci>σ</mml:ci>
4179
<mml:cn>2</mml:cn>
4180
</mml:apply>
4181
</mml:apply>
4182
</mml:apply>
4183
</mml:apply>
4184
</mml:apply>
4185
</mml:apply>
4186
</mml:reln>
4187
</mml:math>
4188
</informalequation>
4189
@end docbook
4190
4191
@noindent
4192
The parameter@tie{}@inlinesigma{}, the argument of
4193
option@tie{}@option{--contrast-edge-scale}, is the length scale on which edges
4194
are detected by @math{g(x, y)}. We apply the Laplacian operator in
4195
Cartesian coordinates
4196
@ifinfo
4197
@display
4198
@math{Delta := Nabla o Nabla = (d^2/dx^2 + d^2/dy^2)}
4199
@end display
4200
@end ifinfo
4201
@html
4202
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4203
<mrow>
4204
<mrow>
4205
<mi>Δ</mi>
4206
</mrow>
4207
<mo>≡</mo>
4208
<mrow>
4209
<mi>∇</mi>
4210
<mo>·</mo>
4211
<mi>∇</mi>
4212
</mrow>
4213
<mo>=</mo>
4214
<mrow>
4215
<mfrac>
4216
<msup>
4217
<mo>∂</mo>
4218
<mn>2</mn>
4219
</msup>
4220
<mrow>
4221
<mo>∂</mo>
4222
<msup>
4223
<mi>x</mi>
4224
<mn>2</mn>
4225
</msup>
4226
</mrow>
4227
</mfrac>
4228
<mo>+</mo>
4229
<mfrac>
4230
<msup>
4231
<mo>∂</mo>
4232
<mn>2</mn>
4233
</msup>
4234
<mrow>
4235
<mo>∂</mo>
4236
<msup>
4237
<mi>y</mi>
4238
<mn>2</mn>
4239
</msup>
4240
</mrow>
4241
</mfrac>
4242
</mrow>
4243
</mrow>
4244
</math>
4245
@end html
4246
@tex
4247
$$
4248
\bigtriangleup \equiv \nabla \cdot \nabla =
4249
{\partial^2 \over \partial x^2} + {\partial^2 \over \partial y^2}
4250
$$
4251
@end tex
4252
@docbook
4253
<informalequation>
4254
<mml:math>
4255
<mml:reln>
4256
<mml:eq/>
4257
<mml:apply>
4258
<mml:laplacian/>
4259
</mml:apply>
4260
<mml:apply>
4261
<mml:scalarproduct/>
4262
<mml:apply>
4263
<mml:grad/>
4264
</mml:apply>
4265
<mml:apply>
4266
<mml:grad/>
4267
</mml:apply>
4268
</mml:apply>
4269
<mml:apply>
4270
<mml:plus/>
4271
<mml:apply>
4272
<mml:partialdiff/>
4273
<mml:bvar>
4274
<mml:ci>x</mml:ci>
4275
<mml:degree>
4276
<mml:cn>2</mml:cn>
4277
</mml:degree>
4278
</mml:bvar>
4279
</mml:apply>
4280
<mml:apply>
4281
<mml:partialdiff/>
4282
<mml:bvar>
4283
<mml:ci>y</mml:ci>
4284
<mml:degree>
4285
<mml:cn>2</mml:cn>
4286
</mml:degree>
4287
</mml:bvar>
4288
</mml:apply>
4289
</mml:apply>
4290
</mml:reln>
4291
</mml:math>
4292
</informalequation>
4293
@end docbook
4294
4295
to @math{g(x, y)}, to arrive at a continuous representation of the
4296
two-dimensional filter kernel
4297
@ifinfo
4298
@display
4299
@math{k(x, y) = (xi^2 - 1) * exp(-xi^2) / (pi * sigma^4),}
4300
@end display
4301
@end ifinfo
4302
@html
4303
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4304
<mrow>
4305
<mrow>
4306
<mi>k</mi>
4307
<mfenced>
4308
<mi>x</mi>
4309
<mi>y</mi>
4310
</mfenced>
4311
</mrow>
4312
<mo>=</mo>
4313
<mrow>
4314
<mfrac>
4315
<mrow>
4316
<msup>
4317
<mi>ξ</mi>
4318
<mn>2</mn>
4319
</msup>
4320
<mo>-</mo>
4321
<mn>1</mn>
4322
</mrow>
4323
<mrow>
4324
<mi>π</mi>
4325
<mo>⁢</mo>
4326
<msup>
4327
<mi>σ</mi>
4328
<mn>4</mn>
4329
</msup>
4330
</mrow>
4331
</mfrac>
4332
<mo>⁢</mo>
4333
<mo>exp</mo>
4334
<mo>⁡</mo>
4335
<mrow>
4336
<mo>(</mo>
4337
<mo>-</mo>
4338
<msup>
4339
<mi>ξ</mi>
4340
<mn>2</mn>
4341
</msup>
4342
<mo>)</mo>
4343
</mrow>
4344
</mrow>
4345
<mtext>,</mtext>
4346
</mrow>
4347
</math>
4348
@end html
4349
@tex
4350
$$
4351
k(x, y) = {{\xi^2 - 1} \over {\pi \sigma^4}} \exp(-\xi^2),
4352
$$
4353
@end tex
4354
@docbook
4355
<informalequation>
4356
<mml:math>
4357
<mml:reln>
4358
<mml:eq/>
4359
<mml:apply>
4360
<mml:ci>k</mml:ci>
4361
<mml:ci>x</mml:ci>
4362
<mml:ci>y</mml:ci>
4363
</mml:apply>
4364
<mml:apply>
4365
<mml:times/>
4366
<mml:apply>
4367
<mml:divide/>
4368
<mml:apply>
4369
<mml:minus/>
4370
<mml:apply>
4371
<mml:power/>
4372
<mml:ci>ξ</mml:ci>
4373
<mml:cn>2</mml:cn>
4374
</mml:apply>
4375
<mml:cn>1</mml:cn>
4376
</mml:apply>
4377
<mml:apply>
4378
<mml:times/>
4379
<mml:csymbol>π</mml:csymbol>
4380
<mml:apply>
4381
<mml:power/>
4382
<mml:ci>σ</mml:ci>
4383
<mml:cn>4</mml:cn>
4384
</mml:apply>
4385
</mml:apply>
4386
</mml:apply>
4387
<mml:apply>
4388
<mml:exp/>
4389
<mml:apply>
4390
<mml:minus/>
4391
<mml:apply>
4392
<mml:power/>
4393
<mml:ci>ξ</mml:ci>
4394
<mml:cn>2</mml:cn>
4395
</mml:apply>
4396
</mml:apply>
4397
</mml:apply>
4398
</mml:apply>
4399
</mml:reln>
4400
</mml:math>
4401
</informalequation>
4402
@end docbook
4403
4404
where we have used the dimensionless distance@tie{}@inlinexi{} from
4405
the origin
4406
@ifinfo
4407
@display
4408
@math{xi^2 = (x^2 + y^2) / (2 * sigma^2).}
4409
@end display
4410
@end ifinfo
4411
@html
4412
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4413
<mrow>
4414
<mrow>
4415
<msup>
4416
<mi>ξ</mi>
4417
<mn>2</mn>
4418
</msup>
4419
</mrow>
4420
<mo>=</mo>
4421
<mrow>
4422
<mfrac>
4423
<mrow>
4424
<msup>
4425
<mi>x</mi>
4426
<mn>2</mn>
4427
</msup>
4428
<mo>+</mo>
4429
<msup>
4430
<mi>y</mi>
4431
<mn>2</mn>
4432
</msup>
4433
</mrow>
4434
<mrow>
4435
<mn>2</mn>
4436
<mo>⁢</mo>
4437
<msup>
4438
<mi>σ</mi>
4439
<mn>2</mn>
4440
</msup>
4441
</mrow>
4442
</mfrac>
4443
</mrow>
4444
<mtext>.</mtext>
4445
</mrow>
4446
</math>
4447
@end html
4448
@tex
4449
$$
4450
\xi^2 = {{x^2 + y^2} \over {2 \sigma^2}}.
4451
$$
4452
@end tex
4453
@docbook
4454
<informalequation>
4455
<mml:math>
4456
<mml:reln>
4457
<mml:eq/>
4458
<mml:apply>
4459
<mml:power/>
4460
<mml:ci>ξ</mml:ci>
4461
<mml:cn>2</mml:cn>
4462
</mml:apply>
4463
<mml:apply>
4464
<mml:divide/>
4465
<mml:apply>
4466
<mml:plus/>
4467
<mml:apply>
4468
<mml:power/>
4469
<mml:ci>x</mml:ci>
4470
<mml:cn>2</mml:cn>
4471
</mml:apply>
4472
<mml:apply>
4473
<mml:power/>
4474
<mml:ci>y</mml:ci>
4475
<mml:cn>2</mml:cn>
4476
</mml:apply>
4477
</mml:apply>
4478
<mml:apply>
4479
<mml:times/>
4480
<mml:cn>2</mml:cn>
4481
<mml:apply>
4482
<mml:power/>
4483
<mml:ci>σ</mml:ci>
4484
<mml:cn>2</mml:cn>
4485
</mml:apply>
4486
</mml:apply>
4487
</mml:apply>
4488
</mml:reln>
4489
</mml:math>
4490
</informalequation>
4491
@end docbook
4492
4493
@noindent
4494
Enfuse uses a discrete approximation of @math{k} in the convolution
4495
with the image. The operator is radially symmetric with respect to
4496
the origin, which is why we can easily plot it in
4497
@ref{Figure:laplacian-of-gaussian}, setting
4498
@ifinfo
4499
@math{R = sqrt(x^2 + y^2)}.
4500
@end ifinfo
4501
@html
4502
<mathinline xmlns="http://www.w3.org/1998/Math/MathML" display="inline">
4503
<mrowinline>
4504
<mi>R</mi>
4505
<mo>=</mo>
4506
<mrowinline>
4507
<msqrtinline>
4508
<msupinline>
4509
<mi>x</mi>
4510
<mn>2</mn>
4511
</msupinline>
4512
<mo>+</mo>
4513
<msupinline>
4514
<mi>y</mi>
4515
<mn>2</mn>
4516
</msupinline>
4517
</msqrtinline>
4518
</mrowinline>
4519
<mtext>.</mtext>
4520
</mrowinline>
4521
</mathinline>
4522
@end html
4523
@tex
4524
$R = \sqrt{x^2 + y^2}$.
4525
@end tex
4526
@docbook
4527
<inlineequation>
4528
<mml:math>
4529
<mml:reln>
4530
<mml:eq/>
4531
<mml:ci>R</mml:ci>
4532
<mml:apply>
4533
<mml:root/>
4534
<mml:degree>
4535
<mml:cn>2</mml:cn>
4536
</mml:degree>
4537
<mml:apply>
4538
<mml:plus/>
4539
<mml:apply>
4540
<mml:power/>
4541
<mml:ci>x</mml:ci>
4542
<mml:cn>2</mml:cn>
4543
</mml:apply>
4544
<mml:apply>
4545
<mml:power/>
4546
<mml:ci>y</mml:ci>
4547
<mml:cn>2</mml:cn>
4548
</mml:apply>
4549
</mml:apply>
4550
</mml:apply>
4551
</mml:reln>
4552
</mml:math>
4553
</inlineequation>
4554
@end docbook
4555
4556
@float Figure,Figure:laplacian-of-gaussian
4557
@vimage{laplacian-of-gaussian}
4558
4559
@caption{Laplacian-of-Gaussian function for @inlinesigma{} = 0.5.}
4560
4561
@shortcaption{Laplacian-of-Gaussian}
4562
@end float
4563
4564
@noindent
4565
See also
4566
@uref{http://@/homepages.inf.ed.ac.uk/@/rbf/@/HIPR2/@/log.htm,
4567
@acronym{HIPR2}: Laplacian of Gaussian}.
4568
4569
Sometimes the @acronym{LoG} is plagued by noise in the input images.
4570
After all, it is a numerical approximation of the second derivative
4571
and deriving always ``roughens'' a function. The (normalized) mask
4572
files relentlessly disclose such problems. Use
4573
option@tie{}@option{--contrast-min-curvature} with a @emph{negative}
4574
argument@tie{}@var{CURVATURE} to suppress all edges with a curvature
4575
below @minus{}@var{CURVATURE} (which is a positive value). Check the
4576
effects with the mask files and particularly the hard-mask files
4577
(@file{@value{src::default-hard-mask-template}}) if using
4578
option@tie{}@option{--hard-mask}.
4579
4580
To indicate the @var{CURVATURE} in relative terms, which is
4581
particularly comprehensible for humans, append a percent sign
4582
(@samp{%}). Try minimum curvatures starting from @minus{}0.5% to
4583
@minus{}3%.
4584
4585
@optionsummaryheading{}
4586
4587
@table @option
4588
@item --contrast-weight
4589
@ref{Fusion Options}
4590
4591
@item --hard-mask
4592
@ref{Fusion Options}
4593
4594
@item --contrast-edge-scale
4595
@ref{Expert Options}
4596
4597
@item --contrast-min-curvature
4598
@ref{Expert Options}
4599
@end table
4600
4601
@node Blend SDev and LoG
4602
@subsection Blend Standard Deviation and Laplacian of Gaussian
4603
@cindex weighting, contrast using a blend of methods
4604
@cindex contrast weighting using a blend of methods
4605
4606
Enfuse can team the standard deviation computation and Laplacian of
4607
Gaussian to deliver the best of both methods. Use a @emph{positive}
4608
argument@tie{}@var{CURVATURE} with option@tie{}@option{--contrast-min-curvature}
4609
to combine both algorithms. In this mode of operation Enfuse computes
4610
the @acronym{SDev}-weight and the @acronym{LoG}-weight, then uses the
4611
@acronym{LoG} to decide whether to go with that value or prefer the
4612
@acronym{SDev} data. If the @acronym{LoG} is greater than
4613
@var{CURVATURE} Enfuse uses the weight delivered by the @acronym{LoG},
4614
otherwise the @acronym{SDev}-weight is rescaled such that its maximum
4615
is equal to @var{CURVATURE}, and the scaled @acronym{SDev} is used as
4616
weight.
4617
4618
This technique merges the two edge detection methods where they are
4619
best. The @acronym{LoG} excels with clear edges and cannot be fooled
4620
by strong but smooth gradients. However, it is bad at detecting faint
4621
edges and it is susceptible to noise. The @acronym{SDev} on the other
4622
hand shines with even the most marginal edges, and resists noise quite
4623
well. Its weakness is that is is easily deceived by strong and smooth
4624
gradients. Tuning @var{CURVATURE} the user can pick the best
4625
threshold for a given set of images.
4626
4627
@optionsummaryheading{}
4628
4629
@table @option
4630
@item --contrast-weight
4631
@ref{Fusion Options}
4632
4633
@item --hard-mask
4634
@ref{Fusion Options}
4635
4636
@item --contrast-window-size
4637
@ref{Expert Options}
4638
4639
@item --gray-projector
4640
@ref{Expert Options}
4641
4642
@item --contrast-edge-scale
4643
@ref{Expert Options}
4644
4645
@item --contrast-min-curvature
4646
@ref{Expert Options}
4647
@end table
4648
4649
4650
@node Scaling and Choice of Mode
4651
@subsection Scaling and Choice of Mode
4652
@cindex scaling of parameters
4653
@cindex mode of operation (@acronym{SDev}, @acronym{LoG}, @dots{})
4654
4655
Experience has shown that neither the parameters @var{EDGESCALE} and
4656
@var{CURVATURE} nor the mode of operation (@acronym{SDev}-only,
4657
@acronym{LoG}-only, or a blend of both) scales to different image
4658
sizes. In practice, this means that if you start with a set of
4659
reduced size images, say 2808@classictimes{}1872 pixels, carefully
4660
optimize @var{EDGESCALE}, @var{CURVATURE} and so on, and find
4661
@acronym{LoG}-only the best mode, and then switch to the original
4662
resolution of 5616@classictimes{}3744 pixels, multiplying (or
4663
dividing) the parameters by four and sticking to @acronym{LoG}-only
4664
might @emph{not} result in the best fused image. For best quality,
4665
perform the parameter optimization and the search for the most
4666
appropriate mode at the final resolution.
4667
4668
4669
@node Local Entropy Weighting
4670
@section Local Entropy Weighting
4671
@cindex weighting, local entropy
4672
4673
Entropy weighting prefers pixels inside a high entropy neighborhood.
4674
4675
@cindex entropy, definition
4676
Let @math{S} be an @math{n}-ary source. Watching the output of
4677
@math{S} an observer on average gains the information
4678
@ifinfo
4679
@display
4680
@math{H_a(n) := sum(p(x) * log_a(1 / p(x)), x in S)}
4681
@end display
4682
@end ifinfo
4683
@html
4684
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4685
<mrow>
4686
<mrow>
4687
<msub>
4688
<mi>H</mi>
4689
<mi>a</mi>
4690
</msub>
4691
<mo>⁡</mo>
4692
<mrow>
4693
<mo>(</mo>
4694
<mi>n</mi>
4695
<mo>)</mo>
4696
</mrow>
4697
</mrow>
4698
<mo>:=</mo>
4699
<mrow>
4700
<munder>
4701
<mo>∑</mo>
4702
<mrow>
4703
<mi>x</mi>
4704
<mo>∈</mo>
4705
<mi>S</mi>
4706
</mrow>
4707
</munder>
4708
<mrow>
4709
<mi>p</mi>
4710
<mo>⁡</mo>
4711
<mrow>
4712
<mo>(</mo>
4713
<mi>x</mi>
4714
<mo>)</mo>
4715
</mrow>
4716
<mo>×</mo>
4717
<mrow>
4718
<msub>
4719
<mtext>log</mtext>
4720
<mi>a</mi>
4721
</msub>
4722
<mo>⁡</mo>
4723
<mrow>
4724
<mo>(</mo>
4725
<mn>1</mn>
4726
<mo>/</mo>
4727
<mrow>
4728
<mi>p</mi>
4729
<mo>⁡</mo>
4730
<mrow>
4731
<mo>(</mo>
4732
<mi>x</mi>
4733
<mo>)</mo>
4734
</mrow>
4735
</mrow>
4736
<mo>)</mo>
4737
</mrow>
4738
</mrow>
4739
</mrow>
4740
</mrow>
4741
</mrow>
4742
</math>
4743
@end html
4744
@tex
4745
$$
4746
H_a(n) := \sum_{x \in S} p(x) \log_a(1 / p(x))
4747
$$
4748
@end tex
4749
@docbook
4750
<informalequation>
4751
<mml:math>
4752
<mml:reln>
4753
<mml:eq/>
4754
<mml:apply>
4755
<mml:apply>
4756
<mml:selector/>
4757
<mml:ci>H</mml:ci>
4758
<mml:ci>a</mml:ci>
4759
</mml:apply>
4760
<mml:ci>n</mml:ci>
4761
</mml:apply>
4762
<mml:apply>
4763
<mml:sum/>
4764
<mml:bvar>
4765
<mml:ci>x</mml:ci>
4766
</mml:bvar>
4767
<mml:condition>
4768
<mml:apply>
4769
<mml:in/>
4770
<mml:ci>x</mml:ci>
4771
<mml:ci>S</mml:ci>
4772
</mml:apply>
4773
</mml:condition>
4774
<mml:apply>
4775
<mml:times/>
4776
<mml:apply>
4777
<mml:ci>p</mml:ci>
4778
<mml:ci>x</mml:ci>
4779
</mml:apply>
4780
<mml:apply>
4781
<mml:log/>
4782
<mml:logbase>
4783
<mml:ci>a</mml:ci>
4784
</mml:logbase>
4785
<mml:apply other='display="scriptstyle"'>
4786
<mml:divide/>
4787
<mml:cn>1</mml:cn>
4788
<mml:apply>
4789
<mml:ci>p</mml:ci>
4790
<mml:ci>x</mml:ci>
4791
</mml:apply>
4792
</mml:apply>
4793
</mml:apply>
4794
</mml:apply>
4795
</mml:apply>
4796
</mml:reln>
4797
</mml:math>
4798
</informalequation>
4799
@end docbook
4800
4801
@cindex entropy
4802
@noindent
4803
per emitted message, where we assume the knowledge of the probability
4804
function@tie{}@math{p(S)}. The expectation value@tie{}@math{H_a(n)}
4805
is called @dfn{entropy} of the source@tie{}@math{S}. Entropy measures
4806
our uncertainty if we are to guess which message gets chosen by the
4807
source in the future. The unit of the entropy depends on the choice
4808
of the constant@tie{}@math{a > 1}. Obviously
4809
@ifinfo
4810
@display
4811
@math{H_b(n) = H_a(n) / log_a(b)}
4812
@end display
4813
@end ifinfo
4814
@html
4815
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4816
<mrow>
4817
<mrow>
4818
<msub>
4819
<mi>H</mi>
4820
<mi>b</mi>
4821
</msub>
4822
<mo>⁡</mo>
4823
<mrow>
4824
<mo>(</mo>
4825
<mi>n</mi>
4826
<mo>)</mo>
4827
</mrow>
4828
</mrow>
4829
<mo>=</mo>
4830
<mrow>
4831
<mrow>
4832
<msub>
4833
<mi>H</mi>
4834
<mi>a</mi>
4835
</msub>
4836
<mo>⁡</mo>
4837
<mrow>
4838
<mo>(</mo>
4839
<mi>n</mi>
4840
<mo>)</mo>
4841
</mrow>
4842
</mrow>
4843
<mo>/</mo>
4844
<mrow>
4845
<msub>
4846
<mtext>log</mtext>
4847
<mi>a</mi>
4848
</msub>
4849
<mo>⁡</mo>
4850
<mrow>
4851
<mo>(</mo>
4852
<mi>b</mi>
4853
<mo>)</mo>
4854
</mrow>
4855
</mrow>
4856
</mrow>
4857
</mrow>
4858
</math>
4859
@end html
4860
@tex
4861
$$
4862
H_b(n) = H_a(n) / \log_a(b)
4863
$$
4864
@end tex
4865
@docbook
4866
<informalequation>
4867
<mml:math>
4868
<mml:reln>
4869
<mml:eq/>
4870
<mml:apply>
4871
<mml:apply>
4872
<mml:selector/>
4873
<mml:ci>H</mml:ci>
4874
<mml:ci>b</mml:ci>
4875
</mml:apply>
4876
<mml:ci>n</mml:ci>
4877
</mml:apply>
4878
<mml:apply>
4879
<mml:divide/>
4880
<mml:apply>
4881
<mml:apply>
4882
<mml:selector/>
4883
<mml:ci>H</mml:ci>
4884
<mml:ci>a</mml:ci>
4885
</mml:apply>
4886
<mml:ci>n</mml:ci>
4887
</mml:apply>
4888
<mml:apply>
4889
<mml:log/>
4890
<mml:logbase>
4891
<mml:ci>a</mml:ci>
4892
</mml:logbase>
4893
<mml:ci>b</mml:ci>
4894
</mml:apply>
4895
</mml:apply>
4896
</mml:reln>
4897
</mml:math>
4898
</informalequation>
4899
@end docbook
4900
4901
@noindent
4902
holds for all @math{b > 1}. We use @math{a = 2} for entropy weighting
4903
and set the entropy of the ``impossible message'' to zero according to
4904
@ifinfo
4905
@display
4906
@math{lim(p * log_a(1 / p), p -> 0) = 0.}
4907
@end display
4908
@end ifinfo
4909
@html
4910
<math xmlns="http://www.w3.org/1998/Math/MathML" display="separate">
4911
<mrow>
4912
<mrow>
4913
<munder>
4914
<mtext>lim</mtext>
4915
<mrow>
4916
<mi>p</mi>
4917
<mo>→</mo>
4918
<mn>0</mn>
4919
</mrow>
4920
</munder>
4921
<mrow>
4922
<mi>p</mi>
4923
<mo>×</mo>
4924
<mrow>
4925
<msub>
4926
<mtext>log</mtext>
4927
<mi>a</mi>
4928
</msub>
4929
<mo>⁡</mo>
4930
<mrow>
4931
<mo>(</mo>
4932
<mn>1</mn>
4933
<mo>/</mo>
4934
<mi>p</mi>
4935
<mo>)</mo>
4936
</mrow>
4937
</mrow>
4938
</mrow>
4939
</mrow>
4940
<mo>=</mo>
4941
<mn>0</mn>
4942
<mtext>.</mtext>
4943
</mrow>
4944
</math>
4945
@end html
4946
@tex
4947
$$
4948
\lim_{p \rightarrow 0} \, p \, \log_a(1 / p) = 0.
4949
$$
4950
@end tex
4951
@docbook
4952
<informalequation>
4953
<mml:math>
4954
<mml:reln>
4955
<mml:eq/>
4956
<mml:apply>
4957
<mml:limit/>
4958
<mml:bvar>
4959
<mml:ci>p</mml:ci>
4960
</mml:bvar>
4961
<mml:condition>
4962
<mml:apply>
4963
<mml:tendsto/>
4964
<mml:ci>p</mml:ci>
4965
<mml:ci>0</mml:ci>
4966
</mml:apply>
4967
</mml:condition>
4968
<mml:apply>
4969
<mml:times/>
4970
<mml:ci>p</mml:ci>
4971
<mml:apply>
4972
<mml:log/>
4973
<mml:logbase>
4974
<mml:ci>a</mml:ci>
4975
</mml:logbase>
4976
<mml:apply>
4977
<mml:divide/>
4978
<mml:cn>1</mml:cn>
4979
<mml:ci>p</mml:ci>
4980
</mml:apply>
4981
</mml:apply>
4982
</mml:apply>
4983
</mml:apply>
4984
<mml:cn>0</mml:cn>
4985
</mml:reln>
4986
</mml:math>
4987
</informalequation>
4988
@end docbook
4989
4990
@noindent
4991
@ref{Figure:entropy} shows an entropy function.
4992
4993
@float Figure,Figure:entropy
4994
@vimage{entropy}
4995
4996
@caption{Entropy function@tie{}H for an experiment with exactly two outcomes.}
4997
4998
@shortcaption{Entropy function}
4999
@end float
5000
5001
For more on (information) entropy visit
5002
@uref{http://@/en.wikipedia.org/@/wiki/@/Information_@/entropy,
5003
Wikipedia}.
5004
5005
Enfuse computes a pixel's entropy by considering the pixel itself and
5006
its surrounding pixels quite similar to @ref{Local Contrast
5007
Weighting}. The size of the window is set by
5008
@option{--entropy-window-size}. Choosing the right size is difficult,
5009
because there is a serious tradeoff between the locality of the data
5010
and the size of the sample used to compute @math{H}. A large window
5011
results in a large sample size and therefore in a reliable entropy,
5012
but considering pixels far away from the center degrades @math{H} into
5013
a non-local measure. For small windows the opposite holds true.
5014
5015
Another difficulty arises from the use of entropy as a weighting
5016
function in dark parts of an image, that is, in areas where the
5017
signal-to-noise ratio is low. Without any precautions, high noise is
5018
taken to be high entropy, which might not be desired. Use
5019
option@tie{}@option{--entropy-cutoff} to control the black level when
5020
computing the entropy.
5021
5022
On the other extreme side of lightness, very light parts of an image,
5023
the sensor might already have overflown without the signal reaching
5024
1.0 in the normalized luminance interval. For these pixels the
5025
entropy is zero and Enfuse can be told of the threshold by properly
5026
setting the second argument of @option{--entropy-cutoff}.
5027
5028
@optionsummaryheading{}
5029
5030
@table @option
5031
@item --entropy-weight
5032
@ref{Fusion Options}
5033
5034
@item --entropy-window-size
5035
@ref{Expert Options}
5036
5037
@item --entropy-cutoff
5038
@ref{Expert Options}
5039
@end table
5040
5041
5042
@node Understanding Masks
5043
@chapter Understanding Masks
5044
@cindex understanding masks
5045
@cindex masks, understanding
5046
5047
@include understanding-masks.texi
5048
5049
5050
@node Tuning Memory Usage
5051
@chapter Tuning Memory Usage
5052
@cindex memory, tuning usage of
5053
@opindex -b
5054
@opindex -m
5055
5056
@include tuning-memory-usage.texi
5057
5058
5059
@node Applications
5060
@chapter Applications of Enfuse
5061
@cindex applications of enfuse
5062
5063
This section describes some of the novel possibilities that Enfuse
5064
offers the photographer. In contrast to the previous chapters, it
5065
centers around the image effects.
5066
5067
@menu
5068
* What Images:: What makes images fusable?
5069
* Repetition:: Just taking the same shot multiple times
5070
* Exposure Series:: Varying the exposure time
5071
* Flash Exposure Series:: Varying the flash output
5072
* Polarization Series:: Changing the polarizer angle
5073
* Focus Stacks:: Stacking images with different in-focus distance
5074
@end menu
5075
5076
@node What Images
5077
@section What Makes Images Fusable?
5078
@cindex images, fusable
5079
5080
Images should align well to be suitable for fusion. However, there is
5081
no hard mathematical rule what ``well'' means. The alignment
5082
requirements for 16@dmn{MPixel} images to yield a sharp
5083
4"@classictimes{}6" print at 300@dmn{dpi} (``dpi'' means dots per
5084
inch) or even for web presentation are relatively low, whereas the
5085
alignment of 8@dmn{MPixel} images for a 12"@classictimes{}18" print
5086
ought to be tight.
5087
5088
@pindex hugin
5089
If the input images need to be aligned, Hugin (@pxref{Helpful
5090
Programs}) is the tool of choice. It produces images exactly in the
5091
format that Enfuse expects.
5092
5093
Sometimes images naturally align extremely well so that no
5094
re-alignment is required. An image series with preprogrammed exposure
5095
steps taken in rapid succession where the camera is mounted on a heavy
5096
tripod and a humongous ball head, mirror lockup, and a cable release
5097
are used, comes to mind.
5098
5099
When in doubt about what will work, try it, and judge for yourself.
5100
5101
@noindent
5102
Useful ideas for a good alignment:
5103
5104
@itemize
5105
@item
5106
Fix all camera parameters that are not explicitly varied.
5107
5108
@table @emph
5109
@item Aperture
5110
Engage full manual (@key{M}) or aperture-priority (@key{A}) mode.
5111
5112
@item Auto-focus
5113
Disable ``Auto Focus''. Be aware that the auto-focus function could
5114
be linked to shutter-release button position ``half pressed'' or to
5115
the shutter release in insidious ways.
5116
5117
@item Closed eyepiece
5118
(This applies only to single lens reflex cameras.) Close the eyepiece
5119
when using a cable release to suppress variations in stray light.
5120
5121
@item Exposure time/Shutter speed
5122
Use the shortest possible exposure time or, in other words, use the
5123
fastest shutter speed to avoid blur caused by camera shake or motion
5124
blur.
5125
5126
@item Flash power
5127
Explicitly control the flash power of @emph{all} flashes. This is
5128
sometimes called ``flash exposure lock''.
5129
5130
@item Sensitivity
5131
Disable ``Auto @acronym{ISO}''.
5132
5133
@item White balance
5134
Disable ``Auto White Balance''. Instead, use the most suitable fixed
5135
white balance or take the white balance off a white card. When in
5136
doubt, use the setting ``Daylight'' or equivalent.
5137
@end table
5138
5139
@item
5140
Steady the camera by any means.
5141
5142
@itemize
5143
@item
5144
Apply your best camera bracing technique combined with controlled
5145
breathing.
5146
5147
@item
5148
Prefer a monopod, or better, a rigid tripod with a heavy head.
5149
5150
@item
5151
Use a cable release if possible.
5152
5153
@item
5154
(This applies to cameras with a moving mirror only.) Engage ``mirror
5155
lockup''.
5156
5157
@item
5158
Consider automatic bracketing when applicable.
5159
5160
@item
5161
Activate camera- or lens-based image stabilization if you are sure
5162
that it improves the image quality in your particular case; otherwise
5163
disengage the feature.
5164
5165
For some lens-based image stabilization systems, it is known that they
5166
``lock'' into different positions every time they are activated.
5167
Moreover, some stabilization systems decrease the image quality when
5168
the lens is mounted on a tripod.
5169
@end itemize
5170
5171
@item
5172
Fire in rapid succession.
5173
@end itemize
5174
5175
@c http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1786
5176
5177
5178
@node Repetition
5179
@section Repetition -- Noise Reduction
5180
@cindex simple series
5181
@cindex series, simple
5182
@cindex noise reduction
5183
5184
@mainpurpose Reduce noise
5185
5186
@noindent
5187
With the default settings, Enfuse computes a weighted average of the
5188
input pixels. For a series of images, repeated with identical
5189
settings, this results in a reduction of (photon shot) noise. In
5190
other words, the dynamic range increases slightly, because the higher
5191
signal-to-noise ratio makes darker shades usable. Furthermore, smooth
5192
or glossy surfaces get a ``cleaner'' look, and edges become visually
5193
sharper. The nitty-gritty reportage look that sometimes stems from a
5194
high sensitivity setting disappears.
5195
5196
Averaged images, and therefore low-noise images, are the base for a
5197
multitude of techniques like, for example, differences. The most
5198
prominent method in this class is dark-frame subtraction.
5199
5200
The defaults set
5201
@samp{--exposure-weight=@value{src::default-weight-exposure}} and
5202
@samp{--saturation-weight=@value{src::default-weight-saturation}}.
5203
Eliminating the saturation component with @samp{--saturation-weight=0.0} can
5204
be worth an extra run.
5205
5206
5207
@node Exposure Series
5208
@section Exposure Series -- Dynamic Range Increase
5209
@cindex exposure series
5210
@cindex series, exposure
5211
@cindex dynamic range increase
5212
5213
@mainpurpose Increase manageable dynamic range
5214
5215
@noindent
5216
An exposure series is a set of images taken with identical parameters
5217
except for the exposure time. Some cameras even provide special
5218
functions to automate recording exposure series. See the instruction
5219
manual of your model for details.
5220
5221
Enfuse's defaults,
5222
@samp{--exposure-weight=@value{src::default-weight-exposure}} and
5223
@samp{--saturation-weight=@value{src::default-weight-saturation}} are
5224
well suited for fusion of @emph{color} images. Remember that
5225
saturation weighting only works for @acronym{RGB} data.
5226
Option@tie{}@option{--saturation-weight} helps to control burnt-out
5227
highlights, as these are heavily desaturated. Alternatively, use
5228
option@tie{}@option{--exposure-cutoff} to suppress noise or blown-out
5229
highlights without altering the overall brightness too much. If no
5230
image suffers from troublesome highlights, the relative saturation
5231
weight can be reduced and even be set to zero.
5232
5233
For black and white images @option{--entropy-weight} can be an
5234
alternative to @option{--saturation-weight} because it suppresses
5235
overexposed pixels, as these contain little information. However,
5236
entropy weighting is not limited to gray-scale data; it has been
5237
successfully applied to @acronym{RGB} images, too. Note that entropy
5238
weighting considers @emph{each} color channel of an @acronym{RGB}
5239
image separately and chooses the channel with the minimum entropy as
5240
representative for the whole pixel.
5241
5242
Enfuse offers the photographer tremendous flexibility in fusing
5243
differently exposed images. Whether you combine only two pictures or
5244
a series of 21, Enfuse imposes no limits on you. Accordingly, the
5245
photographic effects achieved range from subtle to surreal, like the
5246
late 1980s ``Max Headroom'' @acronym{TV}-Series, to really unreal.
5247
Like some time ago in the chemical days of photography, when a new
5248
developer opened unseen possibilities for artists, exposure fusion
5249
extends a photographer's expressive space in the digital age. Whether
5250
the results look good or bad, whether the images are dull or exciting,
5251
is entirely up the artist.
5252
5253
In the next sections we give assistance to starters, and rectify
5254
several misconceptions about Enfuse.
5255
5256
@menu
5257
* Exposure Series Tips:: Some hints for beginners
5258
* Exposure Series Misconceptions:: What works despite the hype
5259
@end menu
5260
5261
5262
@node Exposure Series Tips
5263
@subsection Tips For Beginners
5264
@cindex exposure series, tips for beginners
5265
5266
Here are some tips to get you in business quickly.
5267
5268
@table @emph
5269
@item Include the best single exposure.
5270
Include the exposure you would have taken if you did not use Enfuse in
5271
your series. It gives you a solid starting point. Think of the other
5272
images as augmenting this best single exposure to bring out the light
5273
and dark features you would like to see.
5274
5275
@item Begin with as small a number of images as possible.
5276
Pre-visualizing the results of Enfuse is difficult. The more images
5277
put into the fusion process and the wider their @acronym{EV}-spacing
5278
is, the more challenging visualizing the output image becomes.
5279
Therefore, start off with as few images as possible.
5280
5281
You can take a larger series of images and only use part of it.
5282
5283
@item Start with a moderate @acronym{EV}-spacing.
5284
As has been pointed out in the previous item, a wide
5285
@acronym{EV}-spacing makes pre-visualization harder. So start out
5286
with a spacing of 2/3@dmn{EV} to 1+1/3@dmn{EV}.
5287
@end table
5288
5289
5290
@node Exposure Series Misconceptions
5291
@subsection Common Misconceptions
5292
@cindex exposure series, common misconceptions
5293
5294
Here are some surprisingly common misconceptions about exposure
5295
series.
5296
5297
@table @emph
5298
@item A single image cannot be the source of an exposure series.
5299
@cindex digital blending
5300
@cindex blending exposures
5301
Raw-files in particular lend themselves to be converted multiple times
5302
and the results being fused together. The technique is simpler,
5303
faster, and usually even looks better than
5304
@uref{http://@/luminous-@/landscape.com/@/tutorials/@/digital-@/blending.shtml,
5305
digital blending} (as opposed to using a graduated neutral density
5306
filter) or
5307
@uref{http://@/www.gimpguru.org/@/Tutorials/@/Blending@/Exposures/,
5308
blending exposures} in an image manipulation program. Moreover,
5309
perfect alignment comes free of charge!
5310
5311
@item An exposure series must feature symmetrically-spaced exposures.
5312
Twice wrong! Neither do the exposures have to be ``symmetric'' like
5313
@{0@dmn{EV}, @minus{}2/3@dmn{EV}, +2/3@dmn{EV}@}, nor does the number
5314
of exposures have to be odd. Series like
5315
@{@minus{}1@minus{}1/3@dmn{EV}, @minus{}1/3@dmn{EV}, +1/3@dmn{EV}@} or
5316
@{@minus{}1@dmn{EV}, 1@dmn{EV}@} might be just right. By the way, the
5317
order in which the images were taken does not matter either.
5318
5319
@item An exposure series must cover the whole dynamic range of the scene.
5320
@cindex light probe
5321
If you do not want to cover the whole range, you do not have to. Some
5322
@acronym{HDR} programs require the user to take a light
5323
probe,@footnote{@uref{http://@/www.debevec.org/, Paul E.@tie{}Debevec}
5324
defines: ``A @dfn{light probe} image is an omnidirectional, high
5325
dynamic range image that records the incident illumination conditions
5326
at a particular point in space.''} whereas Enfuse offers the user
5327
complete freedom of exposure.
5328
5329
@item All exposure values must be different.
5330
You can repeat any exposure as often as you like. That way you
5331
combine an exposure series with parts of @ref{Repetition}, emphasizing
5332
the multiply occuring exposures and reducing noise.
5333
@end table
5334
5335
5336
@node Flash Exposure Series
5337
@section Flash Exposure Series -- Directed Lighting
5338
@cindex flash exposure series
5339
@cindex series, flash exposure
5340
@cindex dynamic range increase
5341
5342
@mainpurpose ???
5343
5344
...
5345
5346
5347
@node Polarization Series
5348
@section Polarization Series -- Saturation Enhancement
5349
@cindex polarization series
5350
@cindex series, polarization
5351
@cindex saturation enhancement
5352
5353
@mainpurpose Reflection suppression, saturation enhancement
5354
5355
In the current implementation of Enfuse, it is not possible in general
5356
to fuse a polarization series. Naively abusing
5357
@option{--saturation-weight} will not work.
5358
5359
5360
@node Focus Stacks
5361
@section Focus Stacks -- Depth-of-Field Increase
5362
@cindex focus stacks
5363
@cindex depth-of-focus increase
5364
5365
@mainpurpose Synthetic Depth-of-Field Increase
5366
5367
A @dfn{focus stack} is a series of images where the distance of the
5368
focal plane from the sensor varies. Sloppily speaking, the images
5369
were focussed at different distances. Fusing such a stack increases
5370
the depth-of-field (@acronym{DOF}) beyond the physical limits of
5371
diffraction.
5372
5373
@menu
5374
* Why Focus Stacks:: Why take the hassle?
5375
* Preparing Focus Stacks:: How to get suitable input images
5376
* Local Contrast Based Fusing:: Fundamental command line options
5377
* Basic Focus Stacking:: Simple, standard deviation method
5378
* Advanced Focus Stacking:: Advanced, Laplacian technique
5379
* Expert Stacking:: Tips for focus stacking experts
5380
@end menu
5381
5382
5383
@node Why Focus Stacks
5384
@subsection Why create focus stacks?
5385
@cindex focus stacks, why create them
5386
5387
Given
5388
5389
@itemize
5390
@item
5391
a fixed sensor or film size,
5392
@item
5393
a lens' particular focal length, and
5394
@item
5395
@cindex circle-of-confusion
5396
a notion about ``sharpness'', technically speaking the size of the
5397
circle-of-confusion (@acronym{CoC})
5398
@end itemize
5399
5400
@cindex depth-of-field
5401
@noindent
5402
the photographer controls the depth-of-field with the aperture.
5403
Smaller apertures -- this is larger aperture numbers -- increase the
5404
@acronym{DOF} and vice versa. However, smaller apertures increase
5405
diffraction which in turn renders the image unsharp. So, there is an
5406
optimum aperture where the photographer gets maximum @acronym{DOF}.
5407
Sadly, for some purposes like macro shots it is not enough. One way
5408
out is to combine the sharp parts of images focused at different
5409
distances, thereby artificially increasing the total @acronym{DOF}.
5410
This is exactly what Enfuse can do.
5411
5412
@cindex sweet spot aperture
5413
@cindex aperture, sweet spot
5414
All lenses have a so called ``sweet spot'' aperture, where their
5415
resolution is best. Taking pictures at this aperture, the
5416
photographer squeezes the maximum quality out of the lens. But: the
5417
``sweet spot'' aperture often is only one or two stops away from wide
5418
open. Wouldn't it be great to be able combine these best-possible
5419
images to form one high-quality, sufficient-@acronym{DOF} image?
5420
Welcome to Enfuse's local-contrast selection abilities.
5421
5422
5423
@node Preparing Focus Stacks
5424
@subsection Preparing Focus Stacks
5425
@cindex focus stacks, preparation
5426
5427
We are going to combine images with limited @acronym{DOF} to increase
5428
their in-focus parts. The whole process is about image sharpness.
5429
Therefore, the input images must align very well, not just well, but
5430
very well. For optimum results the maximum control point distance in
5431
Hugin (@pxref{Helpful Programs}) should not exceed
5432
0.3--0.5@dmn{pixels} to ensure perfect blending.
5433
5434
As in all image fusion operations it is preferable to use 16@dmn{bit}
5435
linear (gamma = 1) images throughout, but 8@dmn{bit} gamma encoded
5436
images will do. Naturally, high @acronym{SNR} input data always is
5437
welcome.
5438
5439
5440
@node Local Contrast Based Fusing
5441
@subsection Local Contrast Based Fusing
5442
@cindex local-contrast-based fusing
5443
@cindex fusing, local-contrast-based
5444
@cindex focus stacks, fusing
5445
5446
A bare bones call to Enfuse for focus stacking could look like this.
5447
5448
@example
5449
enfuse \
5450
--exposure-weight=0 \
5451
--saturation-weight=0 \
5452
--contrast-weight=1 \
5453
--hard-mask \
5454
@dots{} \
5455
--output=output.tif \
5456
input-<0000-9999>.tif
5457
@end example
5458
5459
@noindent
5460
Here is what each option causes:
5461
5462
@table @option
5463
@item --exposure-weight=0
5464
Switch @strong{off} exposure based pixel selection. The default
5465
weight is @value{src::default-weight-exposure}.
5466
5467
@item --saturation-weight=0
5468
Switch @strong{off} saturation based pixel selection. The default
5469
weight is @value{src::default-weight-saturation}.
5470
5471
@item --contrast-weight=1
5472
Switch @strong{on} pixel selection based on local contrast.
5473
5474
@item --hard-mask
5475
Select the best pixel from the image stack and ignore all others.
5476
Without this option, Enfuse uses all pixels in the stack and weights
5477
them according to their respective quality, which in our case is local
5478
contrast. Without @option{--hard-mask}, the result will always look a
5479
bit soft. @xref{Local Contrast Weighting}.
5480
@end table
5481
5482
@noindent
5483
If you want to see some entertaining progress messages --
5484
local-contrast weighting takes a while --, also pass the
5485
@option{--verbose}@tie{}option for a verbose progress report.
5486
5487
5488
@node Basic Focus Stacking
5489
@subsection Basic Focus Stacking
5490
@cindex basic focus stacking
5491
@cindex focus stacking, basic
5492
5493
For a large class of image stacks Enfuse's default algorithm, as
5494
selected in @ref{Local Contrast Based Fusing}, to determine the
5495
sharpness produces nice results. The algorithm uses a moving square
5496
window, the so-called contrast window. It computes the standard
5497
deviation of the pixels inside of the window. The program then
5498
selects the window's center pixel of the image in the stack where the
5499
standard deviation is largest, that is, the local contrast reaches the
5500
maximum.
5501
5502
However, the algorithm fails to deliver good masks for images which
5503
exhibit high contrast edges on the scale of the contrast window size.
5504
The typical artifacts that show up are
5505
5506
@itemize
5507
@item
5508
faint dark seams on the light side of the high contrast edges and
5509
5510
@item
5511
extremely soft, slightly lighter seams on the dark side of the high
5512
contrast edges,
5513
@end itemize
5514
5515
@noindent
5516
where the distance of the seams from the middle of the edge is
5517
comparable to the contrast window size.
5518
5519
If your results do not show any of these artifacts, stick with the
5520
basic algorithm. Advanced focus stacking, as described in the next
5521
sections, delivers superior results in case of artifacts, though
5522
requires manually tuning several parameters.
5523
5524
5525
@node Advanced Focus Stacking
5526
@subsection Advanced Focus Stacking
5527
@cindex advanced focus stacking
5528
@cindex focus stacking, advanced
5529
5530
If your fused image shows any of the defects described in the previous
5531
section, you can try a more difficult-to-use algorithm that
5532
effectively works around the seam artifacts. It is described in the
5533
next section.
5534
5535
@menu
5536
* Local Contrast Problem:: What is the problem Kenneth?
5537
* Laplacian Edge Detection:: Using a Laplacian-of-Gaussian to detect edges
5538
* Local Contrast Enhancement:: Boosting local contrast before weighting
5539
* Suppressing Noise or Recognizing Faint Edges:: The best of both worlds
5540
* Focus Stacking Decision Tree:: What to do and how to fuse
5541
@end menu
5542
5543
5544
@node Local Contrast Problem
5545
@subsubsection A Detailed Look at the Problem
5546
@cindex local contrast problem
5547
@cindex problem, local contrast
5548
5549
Let us use an example to illustrate the problem of relating the
5550
sharpness with the local contrast variations. Say we use a
5551
5@classictimes{}5 contrast window. Moreover, let @code{sharp_edge}
5552
and @code{smooth_edge} be two specific configurations:
5553
5554
@example
5555
sharp_edge = [ 0, 0, 200, 0, 0;
5556
0, 225, 0, 0, 0;
5557
0, 255, 0, 0, 0;
5558
215, 0, 0, 0, 0;
5559
200, 0, 0, 0, 0]
5560
@end example
5561
5562
@example
5563
smooth_edge = [ 0, 62, 125, 187, 250;
5564
1, 63, 126, 188, 251;
5565
2, 65, 127, 190, 252;
5566
3, 66, 128, 191, 253;
5567
5, 67, 130, 192, 255]
5568
@end example
5569
5570
where @samp{;} separates the rows and @samp{,} separates the columns.
5571
This is in fact @uref{http://@/www.gnu.org/@/software/@/octave/,
5572
Octave} syntax.
5573
5574
@ref{Figure:sharp-edge} and @ref{Figure:smooth-edge} show plots of the
5575
matrices @code{sharp_edge} and @code{smooth_edge}.
5576
5577
@float Figure,Figure:sharp-edge
5578
@vimage{sharp-edge}
5579
5580
@caption{3D plot augmented by contour plot of the matrix@tie{}@code{sharp_edge}.}
5581
5582
@shortcaption{Sharp edge}
5583
@end float
5584
5585
@float Figure,Figure:smooth-edge
5586
@vimage{smooth-edge}
5587
5588
@caption{3D plot augmented by contour plot of the matrix@tie{}@code{smooth_edge}.}
5589
5590
@shortcaption{Smooth edge}
5591
@end float
5592
5593
@noindent
5594
Our intuition lets us ``see'' an extremely sharp edge in the first
5595
matrix, whereas the second one describes an extraordinarily smooth
5596
diagonal intensity ramp. Which one will be selected? Well,
5597
@code{sharp_edge} has a standard deviation of 88.07 and
5598
@code{smooth_edge} has 88.41. Thus, @code{smooth_edge} wins,
5599
contradicting our intuition, and even worse, our intention!
5600
5601
Sadly, configurations like @code{smooth_edge} occur more often with
5602
high-quality, good
5603
@uref{http://@/www.luminous-@/landscape.com/@/essays/@/bokeh.shtml,
5604
bokeh} lenses. In fact, they are the very manifestation of ``good
5605
bokeh''. Therefore, Laplacian edge detection plays an important role
5606
when working with high-quality lenses.
5607
5608
5609
@node Laplacian Edge Detection
5610
@subsubsection Laplacian Edge Detection
5611
@cindex laplacian edge detection
5612
@cindex edge detection, laplacian
5613
5614
Enfuse provides a Laplacian-based algorithm that can help in
5615
situations where weighting based on the standard deviation fails. It
5616
is activated with a positive value for @var{SCALE} in
5617
@code{--contrast-edge-scale}=@/@var{SCALE}. The Laplacian will detect
5618
two-dimensional @emph{curvature} on the scale of @var{SCALE}. Here
5619
and in the following we simply speak of ``curvature'' where we mean
5620
``magnitude of curvature''. That is, we shall not distinguish between
5621
convex and concave edges. Enfuse always use the magnitude of
5622
curvature for weighting.
5623
5624
Typically, @var{SCALE} ranges between 0.1@dmn{pixels} and
5625
0.5@dmn{pixels}, where 0.3@dmn{pixels} is a good starting point. To
5626
find the best value for @var{SCALE} though, usually some
5627
experimentation will be necessary. Use @option{--save-masks} to get
5628
all soft-mask (default:
5629
@file{@value{src::default-soft-mask-template}}) and hard-mask files
5630
(default: @file{@value{src::default-hard-mask-template}}). Check how
5631
different scales affect the artifacts. Also @pxref{Understanding
5632
Masks}.
5633
5634
5635
@node Local Contrast Enhancement
5636
@subsubsection Local Contrast Enhancement
5637
@cindex local contrast enhancement
5638
@cindex contrast enhancement, local
5639
5640
Sometimes Enfuse misses smoother edges with
5641
@option{--contrast-edge-scale} and a little local contrast enhancement
5642
(@acronym{LCE}) helps. Set
5643
@code{--contrast-edge-scale}=@/@var{SCALE}:@/@var{LCE-SCALE}:@/@var{LCE-FACTOR}.
5644
where @var{LCE-SCALE} and @var{LCE-FACTOR} work like the
5645
@uref{http://@/www.cambridgeincolour.com/@/tutorials/@/unsharp-@/mask.htm,
5646
unsharp mask} filters in various image manipulation programs. Start
5647
with @var{LCE-SCALE} ten times the value of @var{SCALE} and a
5648
@var{LCE-FACTOR} of 2--5.
5649
5650
@var{LCE-SCALE} can be specified as a percentage of @var{SCALE}.
5651
@var{LCE-FACTOR} also can be specified as a percentage. Examples:
5652
5653
@example
5654
--contrast-edge-scale=0.3:3.0:3
5655
--contrast-edge-scale=0.3:1000%:3.0
5656
--contrast-edge-scale=0.3:3:300%
5657
--contrast-edge-scale=0.3:1000%:300%
5658
@end example
5659
5660
@noindent
5661
By default @acronym{LCE} is turned off.
5662
5663
5664
@node Suppressing Noise or Recognizing Faint Edges
5665
@subsubsection Suppressing Noise or Recognizing Faint Edges
5666
@cindex advanced focus stacking, suppressing noise
5667
@cindex advanced focus stacking, recognizing faint edges
5668
5669
The Laplacian-based algorithm is much better at resisting the seam
5670
problem than the local-contrast algorithm, but it has two
5671
shortcomings:
5672
5673
@enumerate
5674
@item
5675
The Laplacian is very susceptible to noise and
5676
@item
5677
it fails to recognize faint edges.
5678
@end enumerate
5679
5680
@noindent
5681
The @option{--contrast-min-curvature} option helps to mitigate both
5682
flaws.
5683
5684
The argument to @code{--contrast-min-curvature}=@var{CURVATURE} either
5685
is an absolute lightness value, for example 0..255 for 8@dmn{bit} data
5686
and 0..65535 for 16@dmn{bit} data, or, when given with a @samp{%}-sign
5687
it is a relative lightness value ranging from 0% to 100%.
5688
5689
To suppress unreal edges or counter excessive noise, use the
5690
@option{--contrast-min-curvature} option with a @emph{negative}
5691
curvature measure @var{CURVATURE}. This forces all curvatures less
5692
than @minus{}@var{CURVATURE} to zero.
5693
5694
A @emph{positive} curvature measure @var{CURVATURE} makes Enfuse merge
5695
the @acronym{LoG} data with the local-contrast data. Every curvature
5696
larger than or equal to @var{CURVATURE} is left unchanged, and every
5697
curvature less than @var{CURVATURE} gets replaced with the rescaled
5698
local-contrast data, such that the largest local contrast is just
5699
below @var{CURVATURE}. This combines the best parts of both
5700
techniques and ensures a precise edge detection over the whole range
5701
of edge curvatures.
5702
5703
@noindent
5704
@strong{Summary}
5705
5706
@table @code
5707
@item -@/-contrast-edge-scale=0.3
5708
Use @acronym{LoG} to detect edges on a scale of 0.3@dmn{pixels}.
5709
Apply the default grayscale projector: @code{average}.
5710
5711
@item -@/-contrast-edge-scale=0.3 -@/-gray-projector=l-star
5712
Use @acronym{LoG} to detect edges on a scale of 0.3@dmn{pixels}.
5713
Apply the L*-grayscale projector.
5714
5715
@item -@/-contrast-edge-scale=0.3:3:300%
5716
Use @acronym{LoG} to detect edges on a scale of 0.3@dmn{pixels},
5717
pre-sharpen the input images by 300% on a scale of 3@dmn{pixels}.
5718
Apply the default grayscale projector: @code{average}.
5719
5720
@item -@/-contrast-edge-scale=0.3 -@/-contrast-min-curvature=@minus{}0.5%
5721
Use @acronym{LoG} to detect edges on a scale of 0.3@dmn{pixels}.
5722
Apply the default grayscale projector: @code{average} and throw away
5723
all edges with a curvature of less than 0.5%.
5724
5725
@item -@/-contrast-edge-scale=0.3 -@/-contrast-min-curvature=0.5% -@/-contrast-window-size=7
5726
Use @acronym{LoG} to detect edges on a scale of 0.3@dmn{pixels}.
5727
Apply the default grayscale projector: @code{average} and throw away
5728
all edges with a curvature of less than 0.5% and replace the
5729
@acronym{LoG} data between 0% and 0.5% with @acronym{SDev} data. Use
5730
a window of 7@classictimes{}7@dmn{pixel} window to compute the
5731
@acronym{SDev}.
5732
@end table
5733
5734
5735
@page
5736
@node Focus Stacking Decision Tree
5737
@subsubsection Focus Stacking Decision Tree
5738
@cindex focus stacking decision tree
5739
@cindex decision tree, focus stacking
5740
5741
@ref{Figure:focus-stacking-decision-tree} helps the user to arrive at
5742
a well-fused focus stack with as few steps as possible.
5743
5744
@float Figure,Figure:focus-stacking-decision-tree
5745
@vimage{focus-stack-decision-tree}
5746
5747
@caption{Focus stacking decision tree.}
5748
5749
@shortcaption{Focus stacking decision tree}
5750
@end float
5751
5752
Always start with the default, contrast weighting with a local
5753
contrast window. Only if seams appear as described in @ref{Advanced
5754
Focus Stacking} switch to Laplacian-of-Gaussian contrast detection.
5755
5756
If some seams remain even in @acronym{LoG}-mode, decrease the
5757
sensitivity of the edge detection with a positive
5758
@option{--contrast-min-curvature}. A too high value of
5759
@option{--contrast-min-curvature} suppresses fine detail though. Part
5760
of the detail can be brought back with pre-sharpening, that is,
5761
@ref{Local Contrast Enhancement} or combining @acronym{LoG} with
5762
local-contrast-window mode by using a negative
5763
@option{--contrast-min-curvature}.
5764
5765
Carefully examining the masks (option@tie{}@option{--save-masks}) that
5766
Enfuse uses helps to judge the effects of the parameters.
5767
5768
5769
@node Expert Stacking
5770
@subsection Tips For Focus Stacking Experts
5771
@cindex expert focus stacking tips
5772
@cindex tips, focus stacking experts
5773
5774
We have collected some advice with which even focus-stacking adepts
5775
can benefit.
5776
5777
@itemize
5778
@item
5779
@cindex sensor, use of clean
5780
Ensure that the sensor is clean.
5781
5782
Aligning focus stacks requires varying the viewing angle, which
5783
corresponds to a changing focal length. Hence, the same pixel on the
5784
sensor gets mapped onto different positions in the final image. Dirt
5785
spots will occur not only once but as many times as there are images
5786
in the stack -- something that is no fun to correct in postprocessing.
5787
5788
@cindex dark frame
5789
@cindex subtraction of dark frame
5790
@cindex hot pixels
5791
@cindex pixels, hot
5792
Along the same lines, the photographer may want to consider to prepare
5793
dark frames before, and possibly also after, the shoot of the focus
5794
stack, to subtract hot pixels before fusion.
5795
5796
@item
5797
@opindex --hard-mask
5798
Prefer a low-sensitivity setting (``@acronym{ISO}'') on the camera to
5799
get low-noise images.
5800
5801
Fusing with @option{--hard-mask} does not average, and thus does not
5802
suppress any noise in the input images.
5803
5804
@item
5805
If the transition of in-focus to out-of-focus areas is too abrupt,
5806
record the images with closest and farthest focusing distances twice:
5807
first with the intended working aperture, and a second time with a
5808
small aperture (large aperture number).
5809
5810
@cindex natural sharp-unsharp transition
5811
@cindex transition, natural sharp-unsharp
5812
The small aperture will give the fused image a more natural in-focus
5813
to out-of-focus transition and the working-aperture shots supply the
5814
detail in the in-focus regions.
5815
@end itemize
5816
5817
5818
@node Helpful Programs
5819
@chapter Helpful Additional Programs
5820
@cindex helpful programs
5821
@cindex programs, helpful additional
5822
5823
@include helpful-programs.texi
5824
5825
5826
@node Bug Reports
5827
@appendix Bug Reports
5828
@cindex bug reports
5829
5830
@include bug-reports.texi
5831
5832
5833
@node Authors
5834
@appendix Authors
5835
@cindex authors, list of
5836
5837
@include authors.texi
5838
5839
5840
@node FDL
5841
@appendix @acronym{GNU} Free Documentation License
5842
@cindex free documentation license (@acronym{FDL})
5843
@cindex @acronym{GNU} free documentation license
5844
5845
@include fdl.texi
5846
5847
5848
@c
5849
@c End of Document
5850
@c
5851
5852
@c The List-of-Tables and List-of-Figures go right before the indices
5853
@c in all formats but TeX. For the TeX output they appear right after
5854
@c the Table-of-Contents.
5855
@ifnotdocbook
5856
@ifnottex
5857
@node List of Tables
5858
@unnumbered List of Tables
5859
@listoffloats Table
5860
5861
5862
@node List of Figures
5863
@unnumbered List of Figures
5864
@listoffloats Figure
5865
@end ifnottex
5866
5867
5868
@node Program Index
5869
@unnumbered Program Index
5870
@cindex program index
5871
@cindex index, program
5872
5873
@printindex pg
5874
5875
5876
@node Syntactic-Comment Index
5877
@unnumbered Syntactic-Comment Index
5878
@cindex syntactic-comment index
5879
@cindex index, syntactic-comment
5880
5881
@printindex sc
5882
5883
5884
@node Option Index
5885
@unnumbered Option Index
5886
@cindex option index
5887
@cindex index, option
5888
5889
@printindex op
5890
5891
5892
@node General Index
5893
@unnumbered General Index
5894
@cindex general index
5895
@cindex index, general
5896
5897
@printindex cp
5898
@end ifnotdocbook
5899
5900
@bye
Loggerhead is a web-based interface for Breezy
Version: 2.0.1