PGMNORM

NAME

      pgmnorm - normalize the contrast in a portable graymap

SYNOPSIS

      pgmnorm [-bpercent <n> | -bvalue <n>] [-wpercent <n> | -wvalue]
      [pgmfile]

DESCRIPTION

      Reads a portable graymap as input.  Normalizes the contrast by forcing
      the lightest pixels to white, the darkest pixels to black, and
      linearly rescaling the ones in between; and produces a portable
      graymap as output.
      By default, the darkest 2 percent of all pixels are mapped to black,
      and the lightest 1 percent are mapped to white.  You can override
      these percentages by using the -bpercent and -wpercent flags, or you
      can specify the exact pixel values to be mapped by using the -bvalue
      and -wvalue flags.  Appropriate numbers for the flags can be gotten
      from the pgmhist tool.
      All flags can be abbreviated to their shortest unique prefix.

DEMONSTRATION

      Let a.pgm be a portable graymap.
      The following command will normalize its constrast:
	pgmmerge pgmnorm a.pgm >anorm.pgm 

BEFORE

AFTER

SEE ALSO

      pgmhist(1), pgm(5)

AUTHOR

      Partially based on the fbnorm filter in Michael Mauldin's "Fuzzy
      Pixmap" package.
      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.