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ppmtopgm(1)


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 output is a "black and white" rendering  of  the  original
   image,  as  in  a black and white photograph.  The quantization formula
   used is .299 r + .587 g + .114 b.

   Note that although there is a pgmtoppm program, it is not necessary for
   simple  conversions  from pgm to ppm , because any ppm program can read
   pgm (and pbm ) files automatically.  pgmtoppm is for colorizing  a  pgm
   file.   Also,  see ppmtorgb3 for a different way of converting color to
   gray.  And ppmdist generates a grayscale image from a color image,  but
   in  a  way that makes it easy to differentiate the original colors, not
   necessarily a way that looks like a black and white photograph.

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.

SEE ALSO

   pgmtoppm(1),ppmtorgb3(1),rgb3toppm(1),ppmdist(1),ppm(5),pgm(5)

AUTHOR

   Copyright (C) 1989 by Jef Poskanzer.

                             10 April 2000                     ppmtopgm(1)



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