pbmtopgm

   Updated: 05 Feb 2003 Table Of Contents

NAME

   pbmtopgm - convert PBM image to PGM by averaging areas

SYNOPSIS

   pbmtopgm width height [pbmfile]

DESCRIPTION

   This program is part of Netpbm.

   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 im-
age. 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.

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

SEE ALSO

   pamditherbw, pnmconvol, pbm, pgm

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 grant-
ed, 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 ex-
press or implied
   warranty.
     _________________________________________________________________



Table Of Contents

     * NAME
     * SYNOPSIS
     * DESCRIPTION
     * SEE ALSO
     * AUTHOR

UNIX/Linux commands referenced on this page:

1. convert
2. as
3. pnmsmooth
4. which
5. pamditherbw
6. pnmconvol