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<title>Pamstereogram User Manual</title>
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<h1>pamstereogram</h1>
<p>Updated: 19 June 2015</p>
<p><a href="#contents">Table Of Contents</a></p>
<h2 id="name">NAME</h2>
<p>pamstereogram - create a single-image stereogram from a PAM
depth map</p>
<h2 id="synopsis">SYNOPSIS</h2>
<p>
<b>pamstereogram</b>
[<b>-help</b>]
[<b>-verbose</b>]
[<b>-blackandwhite</b> | <b>-grayscale</b> | <b>-color</b>]
[<b>-maxval=</b><i>value</i>]
[<b>-patfile=</b><i>pamfile</i>]
[<b>-texfile=</b><i>pamfile</i>]
[<b>-bgcolor=</b><i>color</i>]
[<b>-smoothing=</b><i>pixels</i>]
[<b>-xbegin=</b><i>pixels</i>]
[<b>-xshift=</b><i>pixels</i>]
[<b>-yshift=</b><i>pixels</i>]
[<b>-magnifypat=</b><i>scale</i>]
[<b>-guidetop</b>]
[<b>-guidebottom</b>]
[<b>-guidesize=</b><i>pixels</i>]
[<b>-dpi=</b><i>resolution</i>]
[<b>-crosseyed</b>]
[<b>-makemask</b>]
[<b>-eyesep=</b><i>inches</i>]
[<b>-depth=</b><i>fraction</i>]
[<b>-planes=</b><i>near_pixels</i>,<i>far_pixels</i>]
[<b>-randomseed=</b><i>integer</i>]
[<i>infile</i>]
</p>
<h2 id="description">DESCRIPTION</h2>
<p>This program is part of <a href="index.html">Netpbm</a>.</p>
<p><b>pamstereogram</b> inputs a depth 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. What's exciting about single-image stereograms is that they
don't require special glasses to view, although it does require a bit
of practice to train your eyes to unfocus properly. The
<b>pamstereogram</b> program provides a wealth of control over how the
stereogram is generated, including the following:</p>
<ul>
<li>black and white, grayscale, or color output</li>
<li>single-image random-dot stereograms (SIRDS), single-image
stereograms (SIS) using a tiled image, or mapped-texture stereograms
(MTS)</li>
<li>images targeting a given device resolution and eye separation</li>
<li>optional guide boxes to assist in focusing</li>
<li>the ability to trade off depth levels for easier viewing</li>
<li>choice of wall-eyed or cross-eyed stereograms</li>
</ul>
<p>The output is a PAM image on standard output. Options control
the exact format of the PAM. If you want a PNM (PBM, PGM, or PPM)
image, use <b>pamtopnm</b> on the output. There is no need to convert
if you will use the image as input to a current Netpbm program, but
many other programs don't know what a PAM is.
<p>To make a red/green type of stereogram (that you view with 3-D
glasses) instead, see <b>ppm3d</b>.</p>
<h2 id="options">OPTIONS</h2>
<p>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.</p>
<dl>
<dt><b>-verbose</b></dt>
<dd>Display messages about image sizes and formats and properties
of the stereogram being generated.</dd>
<dt><b>-blackandwhite</b></dt>
<dd>Produce a single-image random-dot black-and-white stereogram.
This is the default.</dd>
<dt><b>-grayscale</b></dt>
<dd>Produce a single-image random-dot grayscale stereogram.</dd>
<dt><b>-color</b></dt>
<dd>Produce a single-image random-dot color stereogram.</dd>
<dt><b>-maxval=</b><i>value</i></dt>
<dd>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 don't specify
<b>-maxval</b>, <b>pamstereogram</b> uses the maxval of the input
image. This option has no effect with <b>-blackandwhite</b>.</dd>
<dt><b>-patfile=</b><i>pamfile</i></dt>
<dd>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
<b>-patfile</b> option along with <b>-blackandwhite</b>,
<b>-grayscale</b>, <b>-color</b>, or <b>-maxval</b>.</dd>
<dt><b>-xbegin=</b><i>pixels</i></dt>
<dd>Specify the horizontal coordinate at which to begin stereogram generation.
The background pattern will be minimally distorted at this point and more
distorted at greater distances. Consider using this in conjunction
with <b>-xshift</b> to align the horizontal start of the pattern with the
horizontal start of stereogram generation. <b>-xbegin</b> is meaningful only
in conjunction with <b>-patfile</b>, <b>-makemask</b>, or <b>-texfile</b>,
and <b>pamstereogram</b> actually ignores it with respect to <b>-texfile</b>
(but may not in a future version of <b>pamstereogram</b>).
<p>The default is to begin in the center.
<p>This option was new in Netpbm 10.71 (June 2015).
<dt><b>-texfile=</b><i>pamfile</i></dt>
<dd>Specify an image to use as the texture for a mapped-texture
stereogram. The idea is that the depth-map image provides the depth
values of the 3-D object/scene while the texture image provides the
true-color values. Consequently, the texture image should align with
the depth-map image. (Note that it's required to have the same
dimensions.) The texture image's background color is ignored when
blending colors.
<p>This option was new in Netpbm 10.53 (December 2010).</p>
</dd>
<dt><b>-bgcolor=</b><i>color</i></dt>
<dd>Use <i>color</i> as the texture image's background color instead
of letting <b>pamstereogram</b> determine it automatically. Specify
the color as described for the
<a href="libppm.html#colorname">argument of the ppm_parsecolor() library
routine</a>. The <b>-bgcolor</b> option is meaningful only in conjunction
with <b>-texfile</b>.
<p>This option was new in Netpbm 10.53 (December 2010).</p>
</dd>
<dt><b>-smoothing=</b><i>pixels</i></dt>
<dd>When used without <b>-texfile</b>, attempt to eliminate artifacts
introduced by edges in the depth map if <i>pixels</i> is greater than zero.
<p>When used with <b>-texfile</b>, horizontally blur non-background
colors into background pixels up to a distance of <i>pixels</i> pixels.
This helps smooth over distracting glitches introduced
by the stereogram's color constraints when producing a mapped-texture
stereogram. In this case, the <b>-smoothing</b> option is helpful
when the texture image includes smooth color transitions (as in a
photograph) but makes crisp texture images (as in a line drawing)
appear blurry.</p>
<p>This option was new in Netpbm 10.53 (December 2010). Before
Netpbm 10.61 (December 2012), it has no effect without <b>-texfile</b>.</p>
</dd>
<dt><b>-xshift=</b><i>pixels</i></dt>
<dd>Shift the pattern image (designated by <b>-patfile</b>) to the
right by <i>pixels</i> pixels (default: 0).
<!-- <b>-xshift</b> is helpful when creating "true-color" stereograms. -->
This option is valid only along with <b>-patfile</b>.</dd>
<dt><b>-yshift</b> <i>pixels</i></dt>
<dd>Shift the pattern image (designated by <b>-patfile</b>)
downwards by <i>pixels</i> pixels (default: 0). This option is
valid only along with <b>-patfile</b>.</dd>
<dt><b>-magnifypat=</b><i>scale</i></dt>
<dd>Magnify each pixel in the pattern file or each random dot by
integral scaling factor <i>scale</i>. Note that
<b>pamstereogram</b> applies the pattern magnification
<em>after</em> pattern shifting (<b>-xshift</b> and
<b>-yshift</b>).</dd>
<dt><b>-guidebottom</b>
<dd>
Draw a pair of 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.
<p>This option was new in Netpbm 10.61 (December 2012). Before that,
the presence of <b>-guidesize</b>, with a positive value, has the same
effect.
</dd>
<dt><b>-guidetop</b>
<dd>
Same as <b>-guidebottom</b>, except the guides go at the top of the image.
<p>This option was new in Netpbm 10.61 (December 2012). Before that,
the presence of <b>-guidesize</b>, with a negative value, has the same
effect.
<dt><b>-guidesize=</b><i>pixels</i></dt>
<dd>The size (width and height) of each guide box.
<p>This is valid only with <b>-guidetop</b> or <b>-guidebottom</b>.
<p>Default is 20.
<p>Before Netpbm 10.61 (December 2012), if you don't specify this option,
<b>pamstereogram</b> draws no guides. If you specify it with a positive
value, <b>pamstereogram</b> behaves as if you specified <b>-guidebottom</b>
too, and if you specify it with a negative value, it behaves as if you
specified <b>-guidetop</b> and specified <b>guidesize</b> with the absolute
value of that negative value.
<dt><b>-dpi=</b><i>resolution</i></dt>
<dd>Specify the resolution of the output device in dots per inch.
The default is 100 DPI, which represents a fairly crisp screen
resolution.
<p>Before Netpbm 10.53 (December 2010), the default was 96 DPI.</p>
</dd>
<dt><b>-crosseyed</b></dt>
<dd>Invert the gray levels in the depth 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 <b>-crosseyed</b> option enables such people to see the 3-D image as
intended. You can also specify the <b>-crosseyed</b> option if you prefer
using depth maps in which darker colors are closer to the eye and lighter
colors are farther from the eye.
<p>Before Netpbm 10.53 (December 2010), <b>pamstereogram</b> used higher
(lighter) numbers for things closer to the eye <em>without</em>
<b>-crosseyed</b> and vice versa.</p>
</dd>
<dt><b>-makemask</b></dt>
<dd>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
<b>-makemask</b> option can be used to help create more
sophisticated pattern files (to use with <b>-patfile</b>) Note that
<b>-makemask</b> ignores <b>-magnifypat</b>; it always produces
masks that assume a pattern magnification of 1.</dd>
<dt><b>-eyesep=</b><i>inches</i></dt>
<dd>Specify the separation in inches between your eyes. The
default, 2.5 inches (6.4 cm), should be sufficient for most people
and probably doesn't need to be changed.</dd>
<dt><b>-depth=</b><i>fraction</i></dt>
<dd>Specify the output image's depth of field. That is,
<i>fraction</i> 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.</dd>
<dt><b>-planes=</b><i>near_pixels</i>,<i>far_pixels</i></dt>
<dd>Explicitly specify the distance between repeated pixels in the near plane
and in the far plane. This is an alternative to
<b>-eyesep</b> and <b>-depth</b>. The following equalities hold:
<ul>
<li><i>eyesep</i> = 2 * <i>far</i></li>
<li><i>depth</i> = 2 * (<i>far</i> − <i>near</i>) /
(2 * <i>far</i> − <i>near</i>)</li>
</ul>
<p>The number of distinct 3-D depths is <i>far</i>
− <i>near</i> + 1. One might say that <b>-eyesep</b>
and <b>-depth</b> are a more human-friendly way to specify stereoscopic
parameters (distance between eyes and tradeoff between perceptibility
and depth) while <b>-planes</b> is a more computer-centric way (pixel
distances in the resulting stereogram).
<p>This option was new in Netpbm 10.59 (June 2012).</p>
</dd>
<dt><b>-randomseed=</b><i>integer</i></dt>
<dd>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.
<p>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 <b>pamstereogram</b>.
<p>This is irrelevant if you use a pattern file (<b>-patfile</b>
option), because there is no random element to <b>pamstereogram</b>'s
behavior.</p>
<p>This option was new in Netpbm 10.32 (February 2006).</p>
</dd>
</dl>
<h2 id="parameters">PARAMETERS</h2>
<p>The only parameter, <i>infile</i>, is the name of an input file
that is a depth map image. If you don't specify <i>infile</i>, the
input is from standard input.</p>
<p>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. Lower (darker) numbers mean further from the eye.
<h2 id="notes">NOTES</h2>
<h3 id="inputimages">Input Images</h3>
<p><b>pamstereogram</b> pays no attention to the image's tuple type and
ignores all planes other than plane 0.</p>
<p>Like any Netpbm program, <b>pamstereogram</b> will accept PNM
input as if it were the PAM equivalent.</p>
<h3 id="mappedtexture">Mapped-texture Stereograms</h3>
<p>In a <i>mapped-texture stereogram</i> (MTS), the 3-D image can be
drawn with true colors. Unlike a SIRDS or tiled-image SIS, however,
the image portrayed by an MTS is apparent in normal 2-D viewing. It
appears repeated multiple times and overlapped with itself, but it is
not hidden.</p>
<p>You create an MTS with <b>pamstereogram</b> by passing the filename
of a PAM "texture image" with a <b>-texfile</b> option. A
texture image portrays the same 3-D object as the depth-map image but
indicates the colors that the program should apply to the object.</p>
<p><b>pamstereogram</b> ignores the texture image's background color when it
overlaps copies of the 3-D object. This prevents, for example, a bright-red
object on a black background from being drawn as a dark-red object (a blend of
50% bright red and 50% black); instead, the program ignores the black and the
object remains bright red. A consequence of this feature is that an MTS looks
best when the objects in the texture image have a crisp outline. Smooth
transitions to the background color result in unwanted color artifacts around
edges because the program ignores only <em>exact</em> matches with the
background color.</p>
<p>You should specify a larger-than-normal value for <b>-eyesep</b>
(and/or <b>-dpi</b>) when producing an MTS. Otherwise, the 3-D object will
repeat so many times that most colored pixels will overlap other colored
pixels, reducing the number of true-colored pixels that remain.</p>
<p>An MTS can employ a background pattern (<b>-patfile</b>). In this
case, <b>pamstereogram</b> replaces background pixels with pattern pixels in
the final step of generating the image.</p>
<h3 id="notes_misc">Miscellaneous</h3>
<p>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
white square on a black background).</p>
<p>With the default values for <b>-dpi</b> and <b>-eyesep</b>, pattern
images that are 128 pixels wide can tile seamlessly.</p>
<h2 id="examples">EXAMPLES</h2>
<p>Generate a SIRDS out of small, brightly colored squares and
prepare it for display on an 87 DPI monitor:</p>
<pre>
pamstereogram depthmap.pam \
-dpi 87 -verbose -color -maxval 1 -magnifypat 3 \
>3d.pam
</pre>
<p>Generate a SIS by tiling a PPM file (a prior run with
<b>-verbose</b> indicates how wide the pattern file should be for
seamless tiling, although any width is acceptable for producing
SISes):</p>
<pre>
pamstereogram depthmap.pam -patfile mypattern.ppm >3d.pam
</pre>
<p>Generate an MTS by associating colors with a depth-mapped object
(using a large eye separation to reduce the number of repetitions of
the texture image) and twice smoothing over background-colored
speckles:</p>
<pre>
pamstereogram depthmap.pam \
-texfile colormap.pam -smoothing 2 -eyesep 3.5 \
>3d.pam
</pre>
<h2 id="seealso">SEE ALSO</h2>
<ul>
<li><a href="pam.html">pam</a></li>
<li><a href="pamsistoaglyph.html">pamsistoaglyph</a></li>
<li><a href="ppm3d.html">ppm3d</a></li>
<li>Harold W. Thimbleby, Stuart Inglis, and Ian H. Witten.
<em>Displaying 3D Images: Algorithms for Single Image Random Dot
Stereograms</em>. In IEEE Computer, <strong>27</strong>(10):38-48,
October 1994. DOI: <a
href="http://dx.doi.org/10.1109/2.318576">10.1109/2.318576</a>.</li>
<li>W. A. Steer.
<em>Stereograms: Technical Details</em>.
URL: <a href="http://www.techmind.org/stereo/stech.html">http://www.techmind.org/stereo/stech.html</a>.</li>
</ul>
<h2><a id="history">HISTORY</a></h2>
<p><b>pamstereogram</b> was new in Netpbm 10.22 (April 2004), but probably
broken beyond usability until Netpbm 10.32 (February 2006) and Netpbm 10.26.23
(January 2006).
<p>A backward incompatible change to the way you request guide boxes
(<b>-guidetop</b>, <b>-guidebottom</b>, <b>-guidesize</b> happened in
Netpbm 10.61 (December 2012).
<h2><a id="author">AUTHOR</a></h2>
<p>Copyright © 2006-2015 Scott Pakin, <a href="mailto:scott+pbm@pakin.org">scott+pbm@pakin.org</a>.</p>
<h2><a id="contents">Table Of Contents</a></h2>
<ul>
<li><a href="#synopsis">SYNOPSIS</a></li>
<li><a href="#description">DESCRIPTION</a></li>
<li><a href="#options">OPTIONS</a></li>
<li><a href="#parameters">PARAMETERS</a></li>
<li><a href="#notes">NOTES</a>
<ul>
<li><a href="#inputimages">Input Images</a></li>
<li><a href="#mappedtexture">Mapped-texture Stereograms</a></li>
<li><a href="#notes_misc">Miscellaneous</a></li>
</ul>
</li>
<li><a href="#examples">EXAMPLES</a></li>
<li><a href="#seealso">SEE ALSO</a></li>
<li><a href="#history">HISTORY</a></li>
<li><a href="#author">AUTHOR</a></li>
</ul>
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