Table Of Contents
NAME
pamstereogram - create a single-image stereogram from a PAM height map
SYNOPSIS
pamstereogram [-help] [-verbose] [-blackandwhite | -grayscale | -color] [-maxval=value] [-patfile=pamfile] [-xshift=pixels] [-yshift=pixels] [-magnifypat=scale] [-guidesize=pixels] [-dpi=resolution] [-crosseyed] [-makemask] [-eyesep=inches] [-depth=fraction] [-randomseed=integer] [infile]
DESCRIPTION
This program is part of Netpbm(1)
pamstereogram inputs a height map (a map of the distances from your eye of the points in a scene) and outputs a single-image stereogram (SIS). A SIS is a 2-D image specially designed to appear three dimensional when viewed with relaxed, slightly unfocused eyes. Whats exciting about single-image stereograms is that they dont require special glasses to view, although it does require a bit of practice to train your eyes to unfocus properly. The pamstereogram program provides a wealth of control over how the stereogram is generated, including the following:
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black and white, grayscale, or color output
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single-image random-dot stereograms (SIRDS) or single-image
stereograms (SIS) using a tiled image
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images targeting a given device resolution and eye
separation
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optional guide boxes to assist in focusing
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the ability to trade off depth levels for easier viewing
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choice of wall-eyed or cross-eyed stereograms
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To make a red/green type of stereogram (that you view with 3-D glasses) instead, see ppm3d.
OPTIONS
You may use either single or double hyphens to denote options. You may use either whitespace or an equals sign to separate an option name from its value.
-verbose | |
Display messages about image sizes and formats and properties
of the stereogram being generated.
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-blackandwhite | |
Produce a single-image random-dot black-and-white stereogram.
This is the default.
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-grayscale | |
Produce a single-image random-dot grayscale stereogram.
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-color | Produce a single-image random-dot color stereogram.
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-maxval=value | |
Designate the maximum value of each gray/color component, i.e.
the color resolution. Smaller values make the output image have
smaller numbers of unique grays/colors. If you dont specify
-maxval, pamstereogram uses the maxval of the input
image. This option has no effect with -blackandwhite.
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-patfile=pnmfile | |
Specify an image to use as a repeated background pattern for
the stereogram instead of a random-dot pattern. Intricate images
generally produce a crisper 3-D effect that simpler images. The
output file will have the same maxval and format (black and white,
grayscale or color) as the pattern file. You cannot specify the
-patfile option along with -blackandwhite,
-grayscale, -color, or -maxval.
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-xshift=pixels | |
Shift the pattern image (designated by -patfile) to the
right by pixels pixels (default: 0).
This option is valid only along with -patfile.
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-yshift pixels | |
Shift the pattern image (designated by -patfile)
downwards by pixels pixels (default: 0). This option is
valid only along with -patfile.
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-magnifypat=scale | |
Magnify each pixel in the pattern file or each random dot by
integral scaling factor scale. Note that
pamstereogram applies the pattern magnification
after pattern shifting (-xshift and
-yshift).
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-guidesize=pixels | |
Draw a pair of pixels by pixels black squares on
a white background underneath the stereogram proper. These squares
help you guide your eyes into proper focus to view the 3-D image.
The trick is to focus your eyes some distance behind the image,
causing you to see four black squares, then continue altering your
focus distance until the middle two black squares fuse into a
single black square. At that point, a crisp, 3-D image will appear.
If pixels is negative, pamstereogram will draw the guide squares above the stereogram instead of below it. If pixels is zero (the default), pamstereogram will draw no guide squares.
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-dpi=resolution | |
Specify the resolution of the output device in dots per inch.
The default is 96 DPI, which represents a fairly crisp screen
resolution.
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-crosseyed | |
Invert the gray levels in the height map (input image) so that
the 3-D image pops out of the page where it would otherwise sink
into the page and vice versa. Some people are unable to diverge
their eyes and can only cross them. The -crosseyed option
enables such people to see the 3-D image as intended.
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-makemask | |
Instead of a stereogram, output a PAM mask image showing
coloring constraints. New pixels will be taken from the pattern
file where the mask is black. Copies of existing pixels will be
taken from the pattern file where the mask is white. The
-makemask option can be used to help create more
sophisticated pattern files (to use with -patfile) Note that
-makemask ignores -magnifypat; it always produces
masks that assume a pattern magnification of 1.
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-eyesep=inches | |
Specify the separation in inches between your eyes. The
default, 2.5 inches (6.4 cm), should be sufficient for most people
and probably doesnt need to be changed.
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-depth=fraction | |
Specify the output images depth of field. That is,
fraction represents the fractional distance of the near
plane from the far plane. Smaller numbers make the 3-D image easier
to perceive but flatter. Larger numbers make the 3-D image more
difficult to perceive but deeper. The default, 0.3333, generally
works fairly well.
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-randomseed=integer | |
Specify a seed to be used for the random number generator.
The default is to use a seed based on the time of day, to one second
granularity.
It is useful to specify the seed if you want to create reproducible results. With the same random seed, you should get identical results every time you run pamstereogram. This is irrelevant if you use a pattern file (-patfile option), because there is no random element to pamstereograms behavior. This option was new in Netpbm 10.32 (February 2006).
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PARAMETERS
The only parameter, infile, is the name of an input file that is a height map image. If you dont specify infile, the input is from standard input.
The input is a PAM image of depth 1. Each sample represents the distance from the eye that the 3-D image at that location should be. Higher numbers mean further from the eye.
pamstereogram pays no attention the the images tuple type and ignores all planes other than plane 0.
Like any Netpbm program, pamstereogram will accept PNM input as if it were the PAM equivalent.
A good initial test is to input an image consisting of a solid shape of distance 0 within a large field of maximum distance (e.g., a black square on a white background).
EXAMPLES
Generate a SIRDS out of small, brightly colored squares and prepare it for display on an 87 DPI monitor: pamstereogram heightmap.pam -dpi 87 -verbose -color -maxval 1 -magnifypat 3 >3d.pam
Generate a SIS by tiling a PPM file (a prior run with -verbose indicates how wide the pattern file should be for seamless tiling, although any width is acceptable for producing SISes): pamstereogram myheights.pam -patfile mypattern.ppm >mysis.pam
SEE ALSO
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Harold W. Thimbleby, Stuart Inglis, and Ian H. Witten.
Displaying 3D Images: Algorithms for Single Image Random Dot
Stereograms. In IEEE Computer, 27(10):38-48,
October 1994. DOI
10.1109/2.318576
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HISTORY
pamstereogram was new in Netpbm 10.22 (April 2004), but probably broken beyond usability until Netpbm 10.32 (Februrary 2006) and Netpbm 10.26.23 (January 2006).
AUTHOR
Copyright (C) 2006 Scott Pakin, scott+pbm@pakin.org.
Table Of Contents
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SYNOPSIS |
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DESCRIPTION |
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OPTIONS |
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PARAMETERS |
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EXAMPLES |
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SEE ALSO |
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HISTORY |
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AUTHOR |