pbmtopgm

pbmtopgm(1)                 General Commands Manual                pbmtopgm(1)

NAME
       pbmtopgm - convert portable bitmap to portable graymap by averaging ar-
       eas

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 surrounding area is a  rectangle  of
       width by height pixels.

       In  other  words, this is a convolution.  pbmtopgm is similar to a spe-
       cial 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  in-
       put) takes PBM input as if it were PGM, with only the mininum and maxi-
       mum 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,  pro-
       vided  that  the  above  copyright notice appear in all copies and that
       both that copyright notice and this permission notice  appear  in  sup-
       porting  documentation.   This software is provided "as is" without ex-
       press or implied warranty.

                                  03 Sep 2001                      pbmtopgm(1)