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pbmtopgm(1) General Commands Manual pbmtopgm(1)
NAME
pbmtopgm - convert portable bitmap to portable graymap by averaging areas
SYNOPSIS
pbmtopgm width height [pbmfile]
DESCRIPTION
pbmtopgm reads a portable bitmap as input. It outputs a portable graymap in which each
pixel's gray level is the average the surrounding black and white input pixels. The sur-
rounding area is a rectangle of width by height pixels.
In other words, this is a convolution. pbmtopgm is similar to a special case of pnmcon-
vol.
You may need a ppmsmooth step after pbmtopgm.
pbmtopgm has the effect of anti-aliasing bitmaps which contain distinct line features.
pbmtopgm works best with odd sample width and heights.
You don't need pbmtopgm just to use a PGM program on a PBM image. Any PGM program (assum-
ing it uses the Netpbm libraries to read the PGM input) takes PBM input as if it were PGM,
with only the mininum and maximum gray levels. So unless your convolution rectangle is
bigger than one pixel, you're not gaining anything with a pbmtopgm step.
SEE ALSO
netpbm(1), pgmtopbm(1), pbm(5)
AUTHOR
Copyright (C) 1990 by Angus Duggan Copyright (C) 1989 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.
03 Sep 2001 pbmtopgm(1)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
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