~scarneiro/ubuntu/oneiric/stereograph/fix-for-755934 : revision 1

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Stereograph for linux, an advanced stereogram generator, v0.30a

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Stereograph comes with ABSOLUTELY NO WARRANTY;

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This is free software under the GPL, and you are welcome to redistribute it

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under certain conditions;

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TABLE OF CONTENTS

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1.0 HOW TO INSTALL THIS PACKAGE

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2.0 WHAT DOES STEREOGRAPH

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2.1 WHY ADVANCED?

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3.0 RENDERER BASICS

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4.0 REDNERING OPTIONS

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5.0 TRANSPARENCY

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6.0 SINGLE IMAGE STEREOGRAMS BASICS

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For a VERY short summary of useful arguments ask the executable.

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1.0 HOW TO INSTALL THIS PACKAGE

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See INSTALL for a short reference. Since release 0.17 libpng is required.

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There should be no problems if this library is installed under /usr/lib.

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Otherwise please take a look to the Makefile and modify it to suit your

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system.

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The current version of Stereograph is available at stereograph.sourceforge.net.

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2.0 WHAT DOES STEREOGRAPH

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Stereograph is a stereogram generator. In detail it is a single image

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stereogram (SIS) generator. That's a program that produces twodimensional

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images that seem to be threedimensional (surely you know the famous works of

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"The Magic Eye", Stereograph produces the same output). You do _not_ need

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any pair of colored spectacles to regard them - everyone can learn it.

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2.1 WHY ADVANCED?

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Yes, that's an interesting question. I know that there are thousands of SIS

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generators available out there. I bought one because I wanted to create

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something special - but I was disappointed when I created my first

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well-prepared composition. The quality was anything but useful. In the third

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dimension (the depth of the image) I was able to see different rough steps

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instead of really smooth transitions as expected. I couldn't believe that. I

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had purchased a professional program that should complete a serious job for me.

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So I took a pencil, a piece of paper and some time to find an optimized way of

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processing stereograms. Stereograph is the result of all my inventions related

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to this this problem. I implemented anti-aliasing for more realistic level

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transitions and to follow exaclty the height structure that is described in the

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base image. I added a zoom feature which has the same effect but is more or less

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not useful for stereograms on a computer screen but interesting for printing.

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Additionally I expanded the depth detail level of 256 levels to 765. If it

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should be one day necessary to increase this level again, there are no limits to

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extend this range up to 24 bits (16.7 millions) or even more.

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I was pointed to tiff which supports floating point precision; I am working on

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this issue.

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3.0 RENDERER BASICS

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-b [base file]

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First of all we begin with a file describing the "relief" of our 3d model.

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The base file should contain all information about our object(s). It is a

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simple graphic where the brightness of a pixel defines its individual

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depth. The darker a pixel is, the more far away it will seem to be in the

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final stereogram - the brighter it is, the closer it will be. Usually only

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gray scale images are used to keep this information. As there are only 256

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tones I decided to terminate this limitation. Of course, any gray scale

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image will be enough for a nice stereogram and can be used with

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stereograph. But if you wanna go for real quality (I mean that quality

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that is needed when you want to render a realistic tree and put an ant on

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it) you can use the full bandwidth of 765 levels by using a special color

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map for rendering (POVRAY does a good job - www.povray.org). Internally

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the RGB values of each pixel are added to calculate the depth.

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-t [texture file]

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everybody identifies with a stereogram the beautiful textures that are

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used to produce themselves. A good texture for a good stereogram needs a

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lot of love and details and some know-how or enough intuitive feelings to

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create one. The texture is that what everyone sees when regarding your

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stereogram - even if he cannot get in the third dimensions of your

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composition. Without an attractive texture you won't invite attractive

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visitors for your personal art work. ;)

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Technical note: the width of the texture stands for the maximum depth of

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any steregram and it cannot be greater than the distance of your two

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eyes - otherwise you won't be able to see anything in your stereogram but

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your beautiful great texture. As a hand rule, 100 should work nice for

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stereograms of 640*480 up to 800*600 pixels. Use 110 to 120 for greater

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ones.

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Hey, the random texture generator is implemented now! See below near '-w'

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-o [output file]

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The file where the stereogram is written to. If it exists stereograph

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won't ask you to allow it to overwrite it, it will simply do it. The

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following file suffices are recognized by Stereograph: tga, png, ppm;

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output to stdout

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if no output file is specified stereograph writes the graphics data to

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stdout.

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-f [output format: tga/png/ppm]

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This optional argument let's you choose the output format Stereograph

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should write. Possible values are: "tga" for 24 bit uncompressed TARGA

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ouput, "png" for 32 bit compressed PNG output and finally "ppm" for

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PPM output; otherwise Stereograph will try to select the output format

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by the suffix of the output file name if there is one.

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4.0 REDNERING OPTIONS

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Quality controling arguments

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-a <1 to 32>

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anti-aliasing

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describes a value between 1 and 32 that declares how many pixels shall

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be calculated by the renderer virtually for ONE pixel. So 1 is the

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absolute minimum, 4 is predefined. You can calculate easily: physically

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you habe n depth levels, where n is the width of the texture used for

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the stereogram. With the AA feature you now have theoretically a*n levels.

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This feature increases _massively_ the color depth of the output file -

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so always try to keep it in true color modes (24 bits or more). I've

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already converted different stereograms processed with AA (7+) to indexed

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ones and couldn't really feel a loss of 3d quality. It's always your

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decision and your former free disk space or net resources, a compromise

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with quality.

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-z <1 to 32>

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zoom

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based on the same idea as AA and has the same effects but physically

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increases the file size. Here 1 the minimum is predefined. It increases

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the width AND the height of the output stereogram by z - so be very

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careful with your free resources, it could end up in a great colorful

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mess...

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btw, for AA and zoom only integer values are expected.

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perspective

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-d <greater than 0.0 up to 8.0>

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distance

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describes the distance of your eyes and the virtual glass that is between

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you and your stereogram. Default value is 5.0 since release 0.30a, feel

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free to walk backwards up to 20.0 steps. 1.0 distance points reflect the

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distance between the screen and the maximum depth.

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-p <greater than 0.0 up to 1.0>

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front factor

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defines the depth of the nearest point (typically mere white). This value

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should be rendered linear which means that for a doubled value depth

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contrast of the scene should be doubled too.

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-e <-1.0..1.0>

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eye shift

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controls the perspective along the x axis (left to right). That is if e is

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positive the image is shifted slightly to the right. The predefined value

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of 0.0 is exactly the centered perspective.

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layout

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-x <0..(base image width) - (texture width) - 1>

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texture instert x

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where the texture is inserted the first time and where the rendering

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process begins its rounds. standard: 0 (left image border);

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-y <0..texture height - 1>

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texture instert y

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y offset of the texture. standard: 0 (top);

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-w <1(theoretically)..texture width/base width - 1>

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this argument specifies the texture width to use for the stereogram. This

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option tells stereograph to generate a random texture or if a texture was

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defined it resizes the texture to match your dimension. This can be very

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useful when rendering transparent stereograms with a lot of different

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textures that all differ in their width. Note that this can only reduce

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the width and stereograph doesn't care about image ratios. It just cuts

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your texture. Random textures cannot be used with transparent rendering.

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-M, -G, -C, S

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use one of there flags to define which color type the random texture

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should conform to. Use -M for monochrome, -G for a grayscale or -C for a

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random color texture. Please note that the random texture feature cannot

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be combined with transparent rendering and that anti-aliasing increases

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the color depth of you image - even if you use a monochrome texture.

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To disable anti-aliasing use '-a 1'.

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The -S flag is experimental - it generates an artistic random texture.

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aid

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-A this flag will add a pair of black triangles at the top of the stereogram

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to make it easier for unexperienced eyes to achieve the magic view.

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base options

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-I inverts a base (non-transparent rendering only);

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-l [level adjust type: none/back/top]

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adjusts the base levels for transparent rendering;

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the keyword 'none' keeps the defined height levels of the base images;

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the keyword 'back' adjusts the bottom area of all upper layers to the

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level defined by the preceding layer;

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the keyword 'top' adjusts the areas of upper layers that are not as far as

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the preceeding layer to the level of the preceding layer;

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disable linear rendering algorithm

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-L this option disables linear rendering

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the anti-artefacts feature

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-R this feature is enabled via the -r flag and tells stereograph to process

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every second line in reversed order to prevent artefacts. This flag should

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be used only with random textures. I am working on a more stealth

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algorithm that could be used with any texture. Please inform me about your

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experiences with this feature! Your feedback is important in the further

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development of this idea because as I know this implementation is really

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unique.

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output types

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-v orders stereograph to tell you everything he's doing;

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5.0 TRANSPARENCY

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Transparent stereograms are rendered in the same way as normal stereograms.

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Stereograph accepts the same parametres, so the only difference for you is to

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define more than one input base file and provide respectively the same number

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of textures. The different bases must have the same dimensions, the textures

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must equal themselves in the width. Otherwise stereograph will complain and

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even not initialize the renderer.

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Since release 0.29a transparent rendering needn't to be enabled via the -T

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flag.

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Example command line:

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> stereograph [ADDITIONAL OPTIONS] -b glass0.png glass1.png glass2.png\

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-t tex0.png tex1.png tex2.png -o glass_demo.png

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or, running on a sh compatible shell you may simply use

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> stereograph [ADDITIONAL OPTIONS] -b $(ls glass?.png) -t $(ls tex?.png)\

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-o glass_demo.png

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At the moment there's no modifier for manipulating the alhpa channels. The

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alphas that may be defined in your png or targa files are ignored.

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This feature is ALPHA. Please inform me about your experiences!

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6.0 SINGLE IMAGE STEREOGRAMS BASICS

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First of all, some basic rules.

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As you can see any stereogram is composed of a texture that is repeated n times

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on a horizontal line but not very regularly. There is a simple rule: the more

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complex the scene, the more complex the resulting stereogram appears and the

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more difficulty it becomes for a human being to regard it in its three

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dimensions. The greater the contrast in the scene, the more artefacts are

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produced as by-product of the rendering process and the fact that not every

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pair of pixels on the screen is unequivocal for our eyes.

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Before we discuss the necessary design properties of the three dimensional

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scene you should know, that the texture design is at least as important as the

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design of the scene. The more details a texture offers the more details from

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your scene the final stereogram can offer to the spectator.

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Finally the nicer your texture the more attractive your artwork becomes for the

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people out there.

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There are a lot of ways to produce a useful scene. For your first steps you can

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simply use a graphics program like the GIMP for example. You will learn how to

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use the different depth values as effective as possible. Put some text in your

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scene to test the ability of detail reproduction of your texture. Not every

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text and every font is readable in a stereogram but feel free to play with it!

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Use small differences in your scene and try to avoid huge contrasts on the

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horizontal line. In vertical direction you can do what you want - this behavior

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won't result in any artifacts that may attack your beautiful stereogram.

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Artifacts result of symmetric pixel distance constellations that result of

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typical height structures of a scene in combination with a typical texture

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constellation. Some shifting of the texture along x or y, some changes in the

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texture or some adjustments of the eye perspective or of the distance could

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correct this. If nothing helps, alter the width of your texture by one or two

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pixels, that should be enough.