Section: User Commands (1)
Updated: 08 August 1989
Reads a portable bitmap as input. Creates a corresponding mask bitmap and writes it out.
The color to be interpreted as "background" is determined automatically. 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 <x> <y> | pnmpaste -or obj <x> <y>
pbmmask obj > objmask pnminvert objmask | pnmpaste -and obj 0 0 > blackback pnmpaste < dest -and objmask <x> <y> | pnmpaste -or blackback <x> <y>
You can also use masks with graymaps and pixmaps, using the pnmarith tool. For instance:
ppmtopgm obj.ppm | pgmtopbm -threshold | pbmmask > objmask.pbm pnmarith -multiply dest.ppm objmask.pbm > t1.ppm pnminvert objmask.pbm | pnmarith -multiply obj.ppm - > t2.ppm pnmarith -add t1.ppm t2.ppm
- 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 tool into a general cellular automaton tool...):
Copyright (C) 1988 by Jef Poskanzer.