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pbmreduce - read a portable bitmap and reduce it N times
pbmreduce [-floyd|-fs|-threshold] [-value <val>]
N [pbmfile]
Reads a portable bitmap as input. Reduces it by a factor of N, and
produces a portable bitmap as output. By default, the halftoning
after the reduction is done via boustrophedonic Floyd-Steinberg error
diffusion; however, the -thresh flag can be used to specify simple
thresholding. This gives better results when reducing line drawings.
The -value flag alters the thresholding value for all quantizations.
It should be a real number between 0 and 1. Above 0.5 means darker
images; below 0.5 means lighter.
All flags can be abbreviated to their shortest unique prefix.
Let a.pbm be a portable bitmap.
The following command will reduce it by a factor of 2 and produce a GIF
file with it:
pbmmerge pbmreduce 2 a.pbm >ared2.pbm | ppmmerge ppmtogif >ared2.gif
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pnmenlarge(1), ppmscale(1), pgmtopbm(1), pbm(5)
Copyright (C) 1988 by Jef Poskanzer.
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation. This software is provided "as is" without
express or implied warranty.