PGMTOPBM

NAME

      pgmtopbm - convert a portable graymap into a portable bitmap

SYNOPSIS

      pgmtopbm [-floyd|-fs | -threshold | -dither8|-d8 |        -cluster3|-
      c3|-cluster4|-c4|-cluster8|-c8] [-value <val>] [pgmfile]

DESCRIPTION

      Reads a portable graymap as input.  Produces a portable bitmap as
      output.  The default quantization method is boustrophedonic Floyd-
      Steinberg error diffusion (-floyd).  Also available are simple
      thresholding; Bayer's ordered dither (-dither8) with a 16x16 matrix;
      three different sizes of 45-degree clustered-dot dither (-cluster3,
      -cluster4, -cluster8);
      Floyd-Steinberg will almost always give the best looking results;
      however, looking good is not always what you want.  For instance,
      thresholding can be used in a pipeline with the ppmconvol tool, for
      tasks like edge and peak detection.  And clustered-dot dithering gives
      a newspaper-ish look, a useful special effect.
      The -value flag alters the thresholding value for Floyd-Steinberg and
      simple threshholding.  It should be a real number between 0 and 1.
      Above 0.5 means darker images; below 0.5 means lighter.
      All flags can be abbreviated to their shortest unique prefix.
      Note that there is no pbmtopgm converter, because any pgm program can
      read pbm files automagically.

REFERENCES

      The only reference you need for this stuff is "Digital Halftoning" by
      Robert Ulichney, MIT Press, ISBN 0-262-21009-6.

SEE ALSO

      pbmreduce(1), pgm(5), pbm(5)

AUTHOR

      Copyright (C) 1989 by Jef Poskanzer.
      Permission to use, copy, modify, and distribute this software and its
      documentation for any purpose and without fee is hereby granted,
      provided that the above copyright notice appear in all copies and that
      both that copyright notice and this permission notice appear in
      supporting documentation.  This software is provided "as is" without
      express or implied warranty.