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)