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<HTML><HEAD><TITLE>Pbmtopgm User Manual</TITLE></HEAD>
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pbmtopgm
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Updated: 05 Feb 2003
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Table Of Contents
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NAME
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pbmtopgm - convert PBM image to PGM by averaging areas
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SYNOPSIS
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pbmtopgm
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width
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height
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[pbmfile]
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DESCRIPTION
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This program is part of Netpbm.
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pbmtopgm reads a PBM image as input. It outputs a PGM image
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in which each pixel's gray level is the average of the surrounding
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black and white input pixels. The surrounding area is a rectangle of
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width by height pixels.
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In other words, this is a convolution. pbmtopgm is similar
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to a special case of pnmconvol.
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You may need a pnmsmooth step after pbmtopgm.
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pbmtopgm has the effect of anti-aliasing bitmaps which
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contain distinct line features.
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pbmtopgm works best with odd sample width and heights.
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You don't need pbmtopgm just to use a PGM program on a PBM
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image. Any PGM program (assuming it uses the Netpbm libraries to read
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the PGM input) takes PBM input as if it were PGM, with only the
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minimum and maximum gray levels. So unless your convolution rectangle
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is bigger than one pixel, you're not gaining anything with a
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pbmtopgm step.
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The opposite transformation (which would turn a PGM into a PBM) is
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dithering. See pamditherbw.
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SEE ALSO
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pamditherbw,
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pnmconvol,
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pbm,
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pgm
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AUTHOR
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Copyright (C) 1990 by Angus Duggan.
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Copyright (C) 1989 by Jef Poskanzer.
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Permission to use, copy, modify, and distribute this software and
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its documentation for any purpose and without fee is hereby granted,
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provided that the above copyright notice appear in all copies and that
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both that copyright notice and this permission notice appear in
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supporting documentation. This software is provided "as is"
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without express or implied warranty.
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Table Of Contents
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NAME
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SYNOPSIS
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DESCRIPTION
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SEE ALSO
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AUTHOR
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</BODY>
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</HTML>
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