Man1 - ppmtopgm.1

ppmtopgm - convert a PPM image to a PGM image

ppmtopgm

[/ppmfile/]

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*(5) , *pgm*(5)

Copyright (C) 1989 by Jef Poskanzer.