1Pbmmask User Manual(0)                                  Pbmmask User Manual(0)
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NAME

6       pbmmask - create a mask bitmap from a regular bitmap
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SYNOPSIS

10       pbmmask [-expand] [pbmfile]
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DESCRIPTION

14       This program is part of Netpbm(1).
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16       pbmmask  reads  a PBM image as input and Generates a corresponding mask
17       of the foreground areas as another PBM image.
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19       The color to be interpreted as  "background"  is  determined  automati‐
20       cally.  Regardless of which color is background, the mask will be white
21       where the background is and black where the figure is.
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23       This lets you do a masked paste like this, for  objects  with  a  black
24       background:
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26           pbmmask obj > objmask
27           pnmpaste < dest -and objmask <x> <y> | pnmpaste -or obj <x> <y>
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29       For  objects with a white background, you can either invert them or add
30       a step:
31           pbmmask obj > objmask
32           pnminvert objmask | pnmpaste -and obj 0 0 > blackback
33           pnmpaste < dest -and objmask <x> <y> | pnmpaste -or blackback <x> <y>
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35       Note that this three-step version works for objects  with  black  back‐
36       grounds too, if you don't care about the wasted time.
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38       You  can  also  use  masks  with  grayscale and color images, using the
39       pnmarith tool.  For instance:
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41           ppmtopgm obj.ppm | pamditherbw -threshold | pbmmask > objmask.pbm
42           pnmarith -multiply dest.ppm objmask.pbm > t1.ppm
43           pnminvert objmask.pbm | pnmarith -multiply obj.ppm - > t2.ppm
44           pnmarith -add t1.ppm t2.ppm
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46       An interesting variation on this is to pipe the mask through  pnmsmooth
47       before  using  it.  This makes the boundary between the two images less
48       sharp.
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OPTIONS

52       -expand
53              Expands the mask by one pixel out from the image.  This is  use‐
54              ful  if  you  want  a little white border around your image.  (A
55              better solution might be to turn the pbmlife program into a gen‐
56              eral cellular automaton tool...)
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SEE ALSO

62       ppmcolormask(1),  pnmpaste(1),  pnminvert(1), pnmarith(1), pnmsmooth(1)
63       pbm(1),
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AUTHOR

67       Copyright (C) 1988 by Jef Poskanzer.
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DOCUMENT SOURCE

70       This manual page was generated by the Netpbm tool 'makeman'  from  HTML
71       source.  The master documentation is at
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73              http://netpbm.sourceforge.net/doc/pbmmask.html
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75netpbm documentation            08 August 1989          Pbmmask User Manual(0)
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