Pamstereogram User Manual(0) Pamstereogram User Manual(0)
Updated:30 December 2012
NAMEpamstereogram - create a single-image stereogram from a PAM depth map
SYNOPSISpamstereogram [-help] [-verbose] [-blackandwhite | -grayscale | -color]
[-maxval=value] [-patfile=pamfile] [-texfile=pamfile] [-bgcolor=color]
[-smoothing=pixels] [-xshift=pixels] [-yshift=pixels] [-magnify‐
pat=scale] [-guidetop] [-guidebottom] [-guidesize=pixels] [-dpi=resolu‐
tion] [-crosseyed] [-makemask] [-eyesep=inches] [-depth=fraction]
[-planes=near_pixels,far_pixels] [-randomseed=integer] [infile]
DESCRIPTION
This program is part of Netpbm(1)pamstereogram 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 pamstereogram program provides a
wealth of control over how the stereogram is generated, including the
following:
· black and white, grayscale, or color output
· single-image random-dot stereograms (SIRDS), single-image stere‐
ograms (SIS) using a tiled image, or mapped-texture stereograms
(MTS)
· images targeting a given device resolution and eye separation
· optional guide boxes to assist in focusing
· the ability to trade off depth levels for easier viewing
· choice of wall-eyed or cross-eyed stereograms
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 pamtopnm 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 pro‐
grams don't know what a PAM is.
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.
-blackandwhite
Produce a single-image random-dot black-and-white stereogram.
This is the default.
-grayscale
Produce a single-image random-dot grayscale stereogram.
-color Produce a single-image random-dot color stereogram.
-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 don't specify
-maxval, pamstereogram uses the maxval of the input image. This
option has no effect with -blackandwhite.
-patfile=pamfile
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 spec‐
ify the -patfile option along with -blackandwhite, -grayscale,
-color, or -maxval.
-texfile=pamfile
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.
This option was new in Netpbm 10.53 (December 2010).
-bgcolor=color
Use color as the texture image's background color instead of
letting pamstereogram determine it automatically. Specify the
color as described for the argument of the ppm_parsecolor()
library routine ⟨libppm.html#colorname⟩ . The -bgcolor option
is meaningful only in conjunction with -texfile.
This option was new in Netpbm 10.53 (December 2010).
-smoothing=pixels
When used without -texfile, attempt to eliminate artifacts
introduced by edges in the depth map if pixels is greater than
zero.
When used with -texfile, horizontally blur non-background colors
into background pixels up to a distance of pixels pixels. This
helps smooth over distracting glitches introduced by the stere‐
ogram's color constraints when producing a mapped-texture stere‐
ogram. In this case, the -smoothing option is helpful when the
texture image includes smooth color transitions (as in a photo‐
graph) but makes crisp texture images (as in a line drawing)
appear blurry.
This option was new in Netpbm 10.53 (December 2010). Before
Netpbm 10.61 (December 2012), it has no effect without -texfile.
-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.
-yshift pixels
Shift the pattern image (designated by -patfile) downwards by
pixels pixels (default: 0). This option is valid only along with
-patfile.
-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).
-guidebottom
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.
This option was new in Netpbm 10.61 (December 2012). Before
that, the presence of -guidesize, with a positive value, has the
same effect.
-guidetop
Same as -guidebottom, except the guides go at the top of the
image.
This option was new in Netpbm 10.61 (December 2012). Before
that, the presence of -guidesize, with a negative value, has the
same effect.
-guidesize=pixels
The size (width and height) of each guide box.
This is valid only with -guidetop or -guidebottom.
Default is 20.
Before Netpbm 10.61 (December 2012), if you don't specify this
option, pamstereogram draws no guides. If you specify it with a
positive value, pamstereogram behaves as if you specified
-guidebottom too, and if you specify it with a negative value,
it behaves as if you specified -guidetop and specified guidesize
with the absolute value of that negative value.
-dpi=resolution
Specify the resolution of the output device in dots per inch.
The default is 100 DPI, which represents a fairly crisp screen
resolution.
Before Netpbm 10.53 (December 2010), the default was 96 DPI.
-crosseyed
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 -crosseyed option
enables such people to see the 3-D image as intended. You can
also specify the -crosseyed option if you prefer using depth
maps in which darker colors are closer to the eye and lighter
colors are farther from the eye.
Before Netpbm 10.53 (December 2010), pamstereogram used higher
(lighter) numbers for things closer to the eye without
-crosseyed and vice versa.
-makemask
Instead of a stereogram, output a PAM mask image showing color‐
ing 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 -magni‐
fypat; it always produces masks that assume a pattern magnifica‐
tion of 1.
-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 doesn't need to be changed.
-depth=fraction
Specify the output image's 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.
-planes=near_pixels,far_pixels
Explicitly specify the distance between repeated pixels in the
near plane and in the far plane. This is an alternative to
-eyesep and -depth. The following equalities hold:
· eyesep = 2 * far
· depth = 2 * (far − near) /
(2 * far − near)
The number of distinct 3-D depths is far − near + 1. One
might say that -eyesep and -depth are a more human-friendly way
to specify stereoscopic parameters (distance between eyes and
tradeoff between perceptibility and depth) while -planes is a
more computer-centric way (pixel distances in the resulting
stereogram).
This option was new in Netpbm 10.59 (June 2012).
-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 repro‐
ducible 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 pamstereogram's behavior.
This option was new in Netpbm 10.32 (February 2006).
PARAMETERS
The only parameter, infile, is the name of an input file that is a
depth map image. If you don't specify infile, the input is from stan‐
dard input.
The input is a PAM image of depth 1. Each sample represents the dis‐
tance from the eye that the 3-D image at that location should be.
Lower (darker) numbers mean further from the eye.
NOTES
Input Images
pamstereogram pays no attention the image's 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.
Mapped-texture Stereograms
In a mapped-texture stereogram (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 hid‐
den.
You create an MTS with pamstereogram by passing the filename of a PAM
<q>texture image</q> with a -texfile 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.
pamstereogram 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 exact matches with the background color.
You should specify a larger-than-normal value for -eyesep (and/or -dpi)
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.
An MTS can employ a background pattern (-patfile). In this case, pam‐
stereogram replaces background pixels with pattern pixels in the final
step of generating the image.
Miscellaneous
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).
With the default values for -dpi and -eyesep, pattern images that are
128 pixels wide can tile seamlessly.
EXAMPLES
Generate a SIRDS out of small, brightly colored squares and prepare it
for display on an 87 DPI monitor:
pamstereogram depthmap.pam \
-dpi 87 -verbose -color -maxval 1 -magnifypat 3 \
>3d.pam
Generate a SIS by tiling a PPM file (a prior run with -verbose indi‐
cates how wide the pattern file should be for seamless tiling, although
any width is acceptable for producing SISes):
pamstereogram depthmap.pam -patfile mypattern.ppm >3d.pam
Generate an MTS by associating colors with a depth-mapped object (using
a large eye separation to reduce the number of repetitions of the tex‐
ture image) and twice smoothing over background-colored speckles:
pamstereogram depthmap.pam \
-texfile colormap.pam -smoothing 2 -eyesep 3.5 \
>3d.pam
SEE ALSO
·
pam(1)
·
pamsistoaglyph(1)
·
ppm3d(1)
· Harold W. Thimbleby, Stuart Inglis, and Ian H. Witten. Display‐
ing 3D Images: Algorithms for Single Image Random Dot Stere‐
ograms. In IEEE Computer, 27(10):38-48, October 1994. DOI
10.1109/2.318576 ⟨http://dx.doi.org/10.1109/2.318576⟩ .
HISTORYpamstereogram 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).
A backward incompatible change to the way you request guide boxes
(-guidetop, -guidebottom, -guidesize happened in Netpbm 10.61 (December
2012).
AUTHOR
Copyright (C) 2006, 2010 Scott Pakin, scott+pbm@pakin.org.
Table Of Contents
·
SYNOPSIS ⟨#synopsis⟩
·
DESCRIPTION ⟨#description⟩
·
OPTIONS ⟨#options⟩
·
PARAMETERS ⟨#parameters⟩
·
NOTES ⟨#notes⟩
·
Input Images ⟨inputimages⟩
·
Mapped-texture Stereograms ⟨mappedtexture⟩
·
Miscellaneous ⟨notes_misc⟩
·
EXAMPLES ⟨#examples⟩
·
SEE ALSO ⟨#seealso⟩
·
HISTORY ⟨#history⟩
·
AUTHOR ⟨#author⟩
netpbm documentation Pamstereogram User Manual(0)
