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

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 ⟨index.html#commonoptions⟩ ), 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