pbmtopgm - convert PBM image to PGM by averaging areas

       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.

       This program is part of Netpbm(1).

       pbmtopgm  reads  a  PBM  image  as input.  It outputs a PGM image in which each pixel's gray level is the
       average of 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 similar to a special case of pnmconvol.

       You may need a pnmsmooth 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 minimum and
       maximum gray levels.  So unless your convolution rectangle is bigger than one pixel, you're  not  gaining
       anything with a pbmtopgm step.

       The opposite transformation (which would turn a PGM into a PBM) is dithering.  See pamditherbw.

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

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

netpbm documentation                               05 Feb 2003                           PbmtopgmUserManual(1)

       pbmtopgm - convert PBM image to PGM by averaging areas

       There are no command line options defined specifically for pbmtopgm, but it recognizes the options common
       to all programs based on libnetpbm (See  Common Options .)

pamditherbw(1), pnmconvol(1), pbm(1), pgm(1)

pbmtopgmwidthheight [pbmfile]