1Pbmtopgm User Manual(0) Pbmtopgm User Manual(0)
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6 pbmtopgm - convert PBM image to PGM by averaging areas
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10 pbmtopgm width height [pbmfile]
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14 This program is part of Netpbm(1).
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16 pbmtopgm reads a PBM image as input. It outputs a PGM image in which
17 each pixel's gray level is the average of the surrounding black and
18 white input pixels. The surrounding area is a rectangle of width by
19 height pixels.
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21 In other words, this is a convolution. pbmtopgm is similar to a spe‐
22 cial case of pnmconvol.
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24 You may need a pnmsmooth step after pbmtopgm.
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26 pbmtopgm has the effect of anti-aliasing bitmaps which contain distinct
27 line features.
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29 pbmtopgm works best with odd sample width and heights.
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31 You don't need pbmtopgm just to use a PGM program on a PBM image. Any
32 PGM program (assuming it uses the Netpbm libraries to read the PGM
33 input) takes PBM input as if it were PGM, with only the minimum and
34 maximum gray levels. So unless your convolution rectangle is bigger
35 than one pixel, you're not gaining anything with a pbmtopgm step.
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37 The opposite transformation (which would turn a PGM into a PBM) is
38 dithering. See pamditherbw.
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42 There are no command line options defined specifically for pbmtopgm,
43 but it recognizes the options common to all programs based on libnetpbm
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45 Common Options ⟨index.html#commonoptions⟩ .)
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49 pamditherbw(1), pnmconvol(1), pbm(1), pgm(1)
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53 Copyright (C) 1990 by Angus Duggan.
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55 Copyright (C) 1989 by Jef Poskanzer.
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57 Permission to use, copy, modify, and distribute this software and its
58 documentation for any purpose and without fee is hereby granted, pro‐
59 vided that the above copyright notice appear in all copies and that
60 both that copyright notice and this permission notice appear in sup‐
61 porting documentation. This software is provided "as is" without
62 express or implied warranty.
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65 This manual page was generated by the Netpbm tool 'makeman' from HTML
66 source. The master documentation is at
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68 http://netpbm.sourceforge.net/doc/pbmtopgm.html
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70netpbm documentation 05 Feb 2003 Pbmtopgm User Manual(0)