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pbmmask Updated: 08 August 1989 Table Of Contents NAME pbmmask - create a mask bitmap from a regular bitmap SYNOPSIS pbmmask [-expand] [pbmfile] DESCRIPTION This program is part of Netpbm. pbmmask reads a PBM image as input and Generates a correspond- ing mask of the foreground areas as another PBM image. The color to be interpreted as "background" is determined au- tomatically. Regardless of which color is background, the mask will be white where the background is and black where the figure is. This lets you do a masked paste like this, for objects with a black background: pbmmask obj > objmask pnmpaste < dest -and objmask| pnmpaste -or obj For objects with a white background, you can either invert them or add a step: pbmmask obj > objmask pnminvert objmask | pnmpaste -and obj 0 0 > blackback pnmpaste < dest -and objmask | pnmpaste -or blackback Note that this three-step version works for objects with black backgrounds too, if you don't care about the wasted time. You can also use masks with graymaps and pixmaps, using the pnmarith tool. For instance: ppmtopgm obj.ppm | pgmtopbm -threshold | pbmmask > obj- mask.pbm pnmarith -multiply dest.ppm objmask.pbm > t1.ppm pnminvert objmask.pbm | pnmarith -multiply obj.ppm - > t2.ppm pnmarith -add t1.ppm t2.ppm An interesting variation on this is to pipe the mask through pnmsmooth before using it. This makes the boundary between the two im- ages less sharp. OPTIONS -expand Expands the mask by one pixel out from the image. This is useful if you want a little white border around your image. (A better solution might be to turn the pbmlife program into a general cellular automaton tool...) SEE ALSO ppmcolormask, pnmpaste, pnminvert, pnmarith, pnmsmooth pbm, AUTHOR Copyright (C) 1988 by Jef Poskanzer. _________________________________________________________________ Table Of Contents * NAME * SYNOPSIS * DESCRIPTION * OPTIONS * SEE ALSO * AUTHOR
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