Ppmtopgm User Manual(0)                                Ppmtopgm User Manual(0)



NAME
       ppmtopgm - convert a PPM image to a PGM image


SYNOPSIS
       ppmtopgm

       [ppmfile]


DESCRIPTION
       This program is part of Netpbm(1)

       ppmtopgm reads a PPM as input and produces a PGM as output.  The output
       is a 'black and white' rendering of the original image, as in a black
       and white photograph.  The quantization formula ppmtopgm uses is g =
       .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.

netpbm documentation             10 April 2000         Ppmtopgm User Manual(0)