1
The Independent JPEG Group's JPEG software
2
==========================================
4
README for release 8b of 16-May-2010
5
====================================
7
This distribution contains the eighth public release of the Independent JPEG
8
Group's free JPEG software. You are welcome to redistribute this software and
9
to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.
11
This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone,
12
Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson,
13
Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers,
14
and other members of the Independent JPEG Group.
16
IJG is not affiliated with the official ISO JPEG standards committee.
22
This file contains the following sections:
24
OVERVIEW General description of JPEG and the IJG software.
25
LEGAL ISSUES Copyright, lack of warranty, terms of distribution.
26
REFERENCES Where to learn more about JPEG.
27
ARCHIVE LOCATIONS Where to find newer versions of this software.
28
ACKNOWLEDGMENTS Special thanks.
29
FILE FORMAT WARS Software *not* to get.
30
TO DO Plans for future IJG releases.
32
Other documentation files in the distribution are:
35
install.txt How to configure and install the IJG software.
36
usage.txt Usage instructions for cjpeg, djpeg, jpegtran,
37
rdjpgcom, and wrjpgcom.
38
*.1 Unix-style man pages for programs (same info as usage.txt).
39
wizard.txt Advanced usage instructions for JPEG wizards only.
40
change.log Version-to-version change highlights.
41
Programmer and internal documentation:
42
libjpeg.txt How to use the JPEG library in your own programs.
43
example.c Sample code for calling the JPEG library.
44
structure.txt Overview of the JPEG library's internal structure.
45
filelist.txt Road map of IJG files.
46
coderules.txt Coding style rules --- please read if you contribute code.
48
Please read at least the files install.txt and usage.txt. Some information
49
can also be found in the JPEG FAQ (Frequently Asked Questions) article. See
50
ARCHIVE LOCATIONS below to find out where to obtain the FAQ article.
52
If you want to understand how the JPEG code works, we suggest reading one or
53
more of the REFERENCES, then looking at the documentation files (in roughly
54
the order listed) before diving into the code.
60
This package contains C software to implement JPEG image encoding, decoding,
61
and transcoding. JPEG (pronounced "jay-peg") is a standardized compression
62
method for full-color and gray-scale images.
64
This software implements JPEG baseline, extended-sequential, and progressive
65
compression processes. Provision is made for supporting all variants of these
66
processes, although some uncommon parameter settings aren't implemented yet.
67
We have made no provision for supporting the hierarchical or lossless
68
processes defined in the standard.
70
We provide a set of library routines for reading and writing JPEG image files,
71
plus two sample applications "cjpeg" and "djpeg", which use the library to
72
perform conversion between JPEG and some other popular image file formats.
73
The library is intended to be reused in other applications.
75
In order to support file conversion and viewing software, we have included
76
considerable functionality beyond the bare JPEG coding/decoding capability;
77
for example, the color quantization modules are not strictly part of JPEG
78
decoding, but they are essential for output to colormapped file formats or
79
colormapped displays. These extra functions can be compiled out of the
80
library if not required for a particular application.
82
We have also included "jpegtran", a utility for lossless transcoding between
83
different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple
84
applications for inserting and extracting textual comments in JFIF files.
86
The emphasis in designing this software has been on achieving portability and
87
flexibility, while also making it fast enough to be useful. In particular,
88
the software is not intended to be read as a tutorial on JPEG. (See the
89
REFERENCES section for introductory material.) Rather, it is intended to
90
be reliable, portable, industrial-strength code. We do not claim to have
91
achieved that goal in every aspect of the software, but we strive for it.
93
We welcome the use of this software as a component of commercial products.
94
No royalty is required, but we do ask for an acknowledgement in product
95
documentation, as described under LEGAL ISSUES.
103
1. We don't promise that this software works. (But if you find any bugs,
105
2. You can use this software for whatever you want. You don't have to pay us.
106
3. You may not pretend that you wrote this software. If you use it in a
107
program, you must acknowledge somewhere in your documentation that
108
you've used the IJG code.
112
The authors make NO WARRANTY or representation, either express or implied,
113
with respect to this software, its quality, accuracy, merchantability, or
114
fitness for a particular purpose. This software is provided "AS IS", and you,
115
its user, assume the entire risk as to its quality and accuracy.
117
This software is copyright (C) 1991-2010, Thomas G. Lane, Guido Vollbeding.
118
All Rights Reserved except as specified below.
120
Permission is hereby granted to use, copy, modify, and distribute this
121
software (or portions thereof) for any purpose, without fee, subject to these
123
(1) If any part of the source code for this software is distributed, then this
124
README file must be included, with this copyright and no-warranty notice
125
unaltered; and any additions, deletions, or changes to the original files
126
must be clearly indicated in accompanying documentation.
127
(2) If only executable code is distributed, then the accompanying
128
documentation must state that "this software is based in part on the work of
129
the Independent JPEG Group".
130
(3) Permission for use of this software is granted only if the user accepts
131
full responsibility for any undesirable consequences; the authors accept
132
NO LIABILITY for damages of any kind.
134
These conditions apply to any software derived from or based on the IJG code,
135
not just to the unmodified library. If you use our work, you ought to
138
Permission is NOT granted for the use of any IJG author's name or company name
139
in advertising or publicity relating to this software or products derived from
140
it. This software may be referred to only as "the Independent JPEG Group's
143
We specifically permit and encourage the use of this software as the basis of
144
commercial products, provided that all warranty or liability claims are
145
assumed by the product vendor.
148
ansi2knr.c is included in this distribution by permission of L. Peter Deutsch,
149
sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA.
150
ansi2knr.c is NOT covered by the above copyright and conditions, but instead
151
by the usual distribution terms of the Free Software Foundation; principally,
152
that you must include source code if you redistribute it. (See the file
153
ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part
154
of any program generated from the IJG code, this does not limit you more than
155
the foregoing paragraphs do.
157
The Unix configuration script "configure" was produced with GNU Autoconf.
158
It is copyright by the Free Software Foundation but is freely distributable.
159
The same holds for its supporting scripts (config.guess, config.sub,
160
ltmain.sh). Another support script, install-sh, is copyright by X Consortium
161
but is also freely distributable.
163
The IJG distribution formerly included code to read and write GIF files.
164
To avoid entanglement with the Unisys LZW patent, GIF reading support has
165
been removed altogether, and the GIF writer has been simplified to produce
166
"uncompressed GIFs". This technique does not use the LZW algorithm; the
167
resulting GIF files are larger than usual, but are readable by all standard
170
We are required to state that
171
"The Graphics Interchange Format(c) is the Copyright property of
172
CompuServe Incorporated. GIF(sm) is a Service Mark property of
173
CompuServe Incorporated."
179
We recommend reading one or more of these references before trying to
180
understand the innards of the JPEG software.
182
The best short technical introduction to the JPEG compression algorithm is
183
Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
184
Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
185
(Adjacent articles in that issue discuss MPEG motion picture compression,
186
applications of JPEG, and related topics.) If you don't have the CACM issue
187
handy, a PostScript file containing a revised version of Wallace's article is
188
available at http://www.ijg.org/files/wallace.ps.gz. The file (actually
189
a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
190
omits the sample images that appeared in CACM, but it includes corrections
191
and some added material. Note: the Wallace article is copyright ACM and IEEE,
192
and it may not be used for commercial purposes.
194
A somewhat less technical, more leisurely introduction to JPEG can be found in
195
"The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by
196
M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides
197
good explanations and example C code for a multitude of compression methods
198
including JPEG. It is an excellent source if you are comfortable reading C
199
code but don't know much about data compression in general. The book's JPEG
200
sample code is far from industrial-strength, but when you are ready to look
201
at a full implementation, you've got one here...
203
The best currently available description of JPEG is the textbook "JPEG Still
204
Image Data Compression Standard" by William B. Pennebaker and Joan L.
205
Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.
206
Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG
207
standards (DIS 10918-1 and draft DIS 10918-2).
208
Although this is by far the most detailed and comprehensive exposition of
209
JPEG publicly available, we point out that it is still missing an explanation
210
of the most essential properties and algorithms of the underlying DCT
212
If you think that you know about DCT-based JPEG after reading this book,
213
then you are in delusion. The real fundamentals and corresponding potential
214
of DCT-based JPEG are not publicly known so far, and that is the reason for
215
all the mistaken developments taking place in the image coding domain.
217
The original JPEG standard is divided into two parts, Part 1 being the actual
218
specification, while Part 2 covers compliance testing methods. Part 1 is
219
titled "Digital Compression and Coding of Continuous-tone Still Images,
220
Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
221
10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of
222
Continuous-tone Still Images, Part 2: Compliance testing" and has document
223
numbers ISO/IEC IS 10918-2, ITU-T T.83.
224
IJG JPEG 8 introduces an implementation of the JPEG SmartScale extension
225
which is specified in a contributed document at ITU and ISO with title "ITU-T
226
JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced Image Coding", April
227
2006, Geneva, Switzerland. The latest version of the document is Revision 3.
229
The JPEG standard does not specify all details of an interchangeable file
230
format. For the omitted details we follow the "JFIF" conventions, revision
231
1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report
232
and thus received a formal publication status. It is available as a free
233
download in PDF format from
234
http://www.ecma-international.org/publications/techreports/E-TR-098.htm.
235
A PostScript version of the JFIF document is available at
236
http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at
237
http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures.
239
The TIFF 6.0 file format specification can be obtained by FTP from
240
ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme
241
found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.
242
IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).
243
Instead, we recommend the JPEG design proposed by TIFF Technical Note #2
244
(Compression tag 7). Copies of this Note can be obtained from
245
http://www.ijg.org/files/. It is expected that the next revision
246
of the TIFF spec will replace the 6.0 JPEG design with the Note's design.
247
Although IJG's own code does not support TIFF/JPEG, the free libtiff library
248
uses our library to implement TIFF/JPEG per the Note.
254
The "official" archive site for this software is www.ijg.org.
255
The most recent released version can always be found there in
256
directory "files". This particular version will be archived as
257
http://www.ijg.org/files/jpegsrc.v8b.tar.gz, and in Windows-compatible
258
"zip" archive format as http://www.ijg.org/files/jpegsr8b.zip.
260
The JPEG FAQ (Frequently Asked Questions) article is a source of some
261
general information about JPEG.
262
It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
263
and other news.answers archive sites, including the official news.answers
264
archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.
265
If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu
267
send usenet/news.answers/jpeg-faq/part1
268
send usenet/news.answers/jpeg-faq/part2
274
Thank to Juergen Bruder for providing me with a copy of the common DCT
275
algorithm article, only to find out that I had come to the same result
276
in a more direct and comprehensible way with a more generative approach.
278
Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the
279
ITU JPEG (Study Group 16) meeting in Geneva, Switzerland.
281
Thank to Thomas Wiegand and Gary Sullivan for inviting me to the
282
Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.
284
Thank to John Korejwa and Massimo Ballerini for inviting me to
285
fruitful consultations in Boston, MA and Milan, Italy.
287
Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther
288
Maier-Gerber, Walter Stoeber, and Fred Schmitz for corresponding
289
business development.
291
Thank to Nico Zschach and Dirk Stelling of the technical support team
292
at the Digital Images company in Halle for providing me with extra
293
equipment for configuration tests.
295
Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful
296
communication about JPEG configuration in Sigma Photo Pro software.
298
Thank to Andrew Finkenstadt for hosting the ijg.org site.
300
Last but not least special thank to Thomas G. Lane for the original
301
design and development of this singular software package.
307
The ISO JPEG standards committee actually promotes different formats like
308
"JPEG 2000" or "JPEG XR" which are incompatible with original DCT-based
309
JPEG and which are based on faulty technologies. IJG therefore does not
310
and will not support such momentary mistakes (see REFERENCES).
311
We have little or no sympathy for the promotion of these formats. Indeed,
312
one of the original reasons for developing this free software was to help
313
force convergence on common, interoperable format standards for JPEG files.
314
Don't use an incompatible file format!
315
(In any case, our decoder will remain capable of reading existing JPEG
316
image files indefinitely.)
322
Version 8 is the first release of a new generation JPEG standard
323
to overcome the limitations of the original JPEG specification.
324
More features are being prepared for coming releases...
326
Please send bug reports, offers of help, etc. to jpeg-info@uc.ag.
added
removed
source/Irrlicht/jpeglib/README
