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(1), pgm(1)


AUTHOR
       Copyright (C) 1989 by Jef Poskanzer.



netpbm documentation		 10 April 2000	       Ppmtopgm User Manual(0)