Ubuntu Manpage: pamsistoaglyph - convert a single-image stereogram to a red/cyan anaglyphic image

Provided by: netpbm_11.10.02-1build1_amd64

NAME

       pamsistoaglyph - convert a single-image stereogram to a red/cyan anaglyphic image

SYNOPSIS

       pamsistoaglyph [--invert] [--sep=number] [--minsep=number] [--gray=number] [in_netpbmfile

       All  options  can  be  abbreviated  to their shortest unique prefix. You may use either white space or an
       equals sign between an option name and its value.

DESCRIPTION

       This program is part of Netpbm(1).

       pamsistoaglyph reads a Netpbm image as input and produces a Netpbm image as output.

       pamsistoaglyph takes a single-image stereogram (SIS) such  as  those  produced  by  pamstereogram(1)  and
       converts  it to a red/cyan anaglyphic image such as those produced by ppm3d(1).  Many people have trouble
       tricking their eyes into focusing beyond the image in front of them and are therefore unable to  perceive
       the  3-D shape hidden within a single-image stereogram.  Anaglyphic stereograms are easier to perceive in
       3-D but require a pair of red/cyan glasses such as those often used to watch  3-D  movies.  The  goal  of
       pamsistoaglyph is to help people who have trouble viewing single-image stereograms see the intriguing 3-D
       effect.

       pamsistoaglyph  can  convert single-image random-dot stereograms (SIRDS), wallpaper stereograms, and even
       dual-image stereograms to anaglyphic images.

OPTIONS

In addition to the options common to all programs based on libnetpbm (most notably -quiet, see Common
Options ), pamsistoaglyph recognizes the following command line options:

For most images, no command-line options need to be specified. The following options are available,
however, for unusual circumstances.

--invert
Swap the left- and right-eye
images. pamsistoaglyph assumes that its input
represents a wall-eyed stereogram and generates the anaglyphic
image accordingly. If the generated image appears to recede into
the page where it should pop out of the page (and vice versa),
this typically implies that the input image represents a
cross-eyed stereogram. Use --invert to correct
the image depth.

--sep=number
Specify the distance in pixels between the left- and right-eye
images. Essentially, this corresponds to the distance between
repetitions of the background pattern. The --sep
option should rarely be necessary
as pamsistoaglyph is fairly good at determining
automatically the eye-separation distance.

--minsep=number
This option is similar to --sep but
constrains pamsistoaglyph only to
a minimum eye-separation distance. Any distance larger
than number is acceptable. The --minsep
option should rarely be necessary
as pamsistoaglyph is fairly good at determining
automatically the eye-separation distance. The default value for
the minimum eye-separation distance is 10% of the image width;
this value seems to work well in practice.

--gray=number
Limit the number of gray levels to use when searching for the
optimal eye-separation
distance. Because pamsistoaglyph looks for
repeated patterns, it is vulnerable to being confused by slight
variations in color. By reducing the input image to grayscale and
capping the number of gray levels,
pamsistoaglyph ameliorates the effects of
unintentional color variations (such as those caused by conversion
from a low-quality JPEG image, for example). The default of 63
seems to work well so the --gray option should
rarely be necessary.

NOTES

       The registration algorithm used by pamsistoaglyph was developed specifically for this program. As far  as
       the  author  knows,  there  are  no  existing  algorithms  for  converting stereograms to anaglyphs.  The
       algorithm works as follows:

       •      Convert the image to grayscale to increase the ability to identify
                  matches.

       •      Count the number of pixels that match N pixels ahead in the
                  image for all N in [1, width/2].

       •      Maintain a running mean (mu) and standard deviation (sigma) of
                  the number of matched pixels.

       •      Store the N corresponding to each spike in the number of
                  matched pixels. A spike is defined as a tally that exceeds the
                  mean plus one, two, or three standard deviations. Only the first
                  spike of a given standard-deviation multiplier is stored.

       •      If a tally greater than mu+3sigma was encountered, return the
                  corresponding N. If not, then if a tally greater than
                  mu+2sigma was encountered, return the
                  corresponding N. If not, then if a tally greater than
                  mu+sigma was encountered, return the
                  corresponding N. If not, then return the N that
                  produces the minimum average distance between matched pixels
                  (i.e., #matches divided by #pixels). If no
                  such N exceeds the minimum allowable eye-separation value,
                  return zero to indicate failure.

       •      If the algorithm returned zero, rerun the algorithm independently
                  on each row of the input image and return the median of
                  all N that exceed the minimum allowable eye-separation
                  value. If no such N exists, abort with an error
                  message.

HISTORY

       Scott Pakin wrote pamsistoaglyph in April 2009.  It first appeared  in  Netpbm  in  Release  10.47  (June
       2009).

AUTHOR

       Copyright (C) 2009 Scott Pakin, scott+pbm@pakin.org

DOCUMENT SOURCE

       This  manual  page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation
       is at

              http://netpbm.sourceforge.net/doc/pamsistoaglyph.html

netpbm documentation                              05 April 2009                    Pamsistoaglyph User Manual(1)