1Pbmmask User Manual(0) Pbmmask User Manual(0)
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6 pbmmask - create a mask bitmap from a regular bitmap
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10 pbmmask [-expand] [pbmfile]
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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 This is probably obsoleted by pambackground.
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22 The color to be interpreted as "background" is determined automati‐
23 cally. Regardless of which color is background, the mask will be white
24 where the background is and black where the figure is.
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26 This lets you do a masked paste like this, for objects with a black
27 background:
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29 pbmmask obj > objmask
30 pnmpaste < dest -and objmask <x> <y> | pnmpaste -or obj <x> <y>
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33 For objects with a white background, you can either invert them or add
34 a step:
35 pbmmask obj > objmask
36 pnminvert objmask | pnmpaste -and obj 0 0 > blackback
37 pnmpaste < dest -and objmask <x> <y> | pnmpaste -or blackback <x> <y>
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40 Note that this three-step version works for objects with black back‐
41 grounds too, if you don't care about the wasted time.
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43 You can also use masks with grayscale and color images, using the pn‐
44 marith tool. For instance:
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46 ppmtopgm obj.ppm | pamditherbw -threshold | pbmmask > objmask.pbm
47 pnmarith -multiply dest.ppm objmask.pbm > t1.ppm
48 pnminvert objmask.pbm | pnmarith -multiply obj.ppm - > t2.ppm
49 pnmarith -add t1.ppm t2.ppm
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52 An interesting variation on this is to pipe the mask through pnmsmooth
53 before using it. This makes the boundary between the two images less
54 sharp.
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58 In addition to the options common to all programs based on libnetpbm
59 (most notably -quiet, see
60 Common Options ⟨index.html#commonoptions⟩ ), pbmmask recognizes the
61 following command line option:
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65 -expand
66 Expands the mask by one pixel out from the image. This is use‐
67 ful if you want a little white border around your image. (A
68 better solution might be to turn the pbmlife program into a gen‐
69 eral cellular automaton tool...)
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75 pambackground(1) ppmcolormask(1), pnmpaste(1), pnminvert(1), pn‐
76 marith(1), pnmsmooth(1) pbm(1),
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80 Copyright (C) 1988 by Jef Poskanzer.
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84 pbmmask is one of the oldest programs in Netpbm. In September 2021,
85 the date on this manual was August 8, 1989 (being the date of the
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87 substantial update). We updated the page then just to add this his‐
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89 information and recommend pambackground.
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91 It is likely that when Bryan wrote pambackground in 2006, he was
92 unaware pbmmask existed. Otherwise, he would presumably have
93 replaced pbmmask with a wrapper around pambackground.
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96 This manual page was generated by the Netpbm tool 'makeman' from HTML
97 source. The master documentation is at
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99 http://netpbm.sourceforge.net/doc/pbmmask.html
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101netpbm documentation 28 September 2021 Pbmmask User Manual(0)