ppmtopgm man page
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.
This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master documentation is at
jpegtopnm(1), pamrecolor(1), pamthreshold(1), pamtopnm(1), pgmtoppm(1), pnmtopclxl(1), pnmtops(1), ppmdist(1), ppmrough(1), ppmtorgb3(1), rgb3toppm(1).