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


       ppmtopgm - convert a PPM image to a PGM image





       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.


       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.


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


       Copyright (C) 1989 by Jef Poskanzer.

netpbm documentation             10 April 2000         Ppmtopgm User Manual(0)

Man(1) output converted with man2html