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