man > pbmtopgm(1)

Pbmtopgm User Manual(1)                General Commands Manual               Pbmtopgm User Manual(1)

NAME
       pbmtopgm - convert PBM image to PGM by averaging areas


SYNOPSIS
       pbmtopgm width height [pbmfile]


DESCRIPTION
       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.


OPTIONS
       There are no command line options defined specifically for pbmtopgm, but  it  recognizes  the
       options common to all programs based on libnetpbm (See ]8;;index.html#commonoptions\ Common Options]8;;\ .)


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


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  support‐
       ing documentation.  This software is provided "as is" without express or implied warranty.

DOCUMENT SOURCE
       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                     Pbmtopgm User Manual(1)