PPMTOPGM

NAME

      ppmtopgm - convert a portable pixmap into a portable graymap

SYNOPSIS

      ppmtopgm [ppmfile] 

DESCRIPTION

      Reads a portable pixmap as input.  Produces a portable graymap as
      output.  The quantization formula used is .299 r + .587 g + .114 b.
      Note that there is no pgmtoppm converter because any ppm program can
      read pgm (and pbm) files automagically.

QUOTE

      Cold-hearted orb that rules the night
      Removes the colors from our sight
      Red is gray, and yellow white
      But we decide which is right
      And which is a quantization error.

DEMONSTRATION

      Let a.gif be a color picture.
      The following command will convert a color GIF file into a grayscale
      one:
            pnmmerge giftopnm a.gif | ppmmerge ppmtopgm | ppmmerge ppmtogif
            > a_gray.gif     

BEFORE

AFTER

SEE ALSO

      ppm(5), pgm(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.