pbmtopgm(1)pbmtopgm(1)NAMEpbmtopgm - convert PBM image to PGM by averaging areas
SYNOPSISpbmtopgm width height [pbmfile]
DESCRIPTIONpbmtopgm 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
surrounding area is a rectangle of width by height pixels.
In other words, this is a convolution. pbmtopgm is simi
lar to a special case of pnmconvol.
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 (assuming 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 ALSOnetpbm(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 soft
ware 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)
