Manual: ppmtopgm

Ppmtopgm User Manual(1)				   General Commands Manual			     Ppmtopgm User Manual(1)

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 output.  The output is a "black and white" rendering of the orig‐
       inal image, as in a black and white photograph.	The quantization formula ppmtopgm uses is y = .299 r + .587 g + .114
       b.

       The  dimensions	and  maxval of the output are the same as the input.  Note that with only one color plane, there are
       far fewer brightnesses that can be represented with the same maxval than with three color planes, so you may want  to
       increase	 the maxval of the input with pamdepth before giving it to ppmtopgm to avoid loss of information.  For exam‐
       ple, with a maxval of 1, there are 8 brightnesses that are possible in a PPM (though some of them are barely  distin‐
       guishable), but only 2 brightness levels possible in a PGM.

       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	ppm‐
       torgb3  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.

OPTIONS
       There are no command line options defined specifically for ppmtopgm, but it recognizes the options common to all pro‐
       grams based on libnetpbm (See  Common Options .)

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.

DOCUMENT SOURCE
       This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation is at

	      http://netpbm.sourceforge.net/doc/ppmtopgm.html

netpbm documentation					25 June 2017				     Ppmtopgm User Manual(1)