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



Table Of Contents


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 out-
       put.  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)
