pbmmask
create a mask bitmap from a regular bitmap
see also :
ppmcolormask - pnmpaste - pnminvert - pnmarith - pnmsmooth
Synopsis
pbmmask
[-expand] [pbmfile]
add an example, a script, a trick and tips
examples
no example yet ...
... Feel free to add your own example above to help other Linux-lovers !
description
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>
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 <x> <y> |
pnmpaste -or blackback <x> <y>
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 >
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
An interesting variation on this is to pipe the mask through
the pnmsmooth script before using it. This makes the
boundary between the two images 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 tool into a general cellular
automaton tool...)
see also
ppmcolormask ,
pnmpaste , pnminvert , pbm,
pnmarith , pnmsmooth
author
Copyright (C)
1988 by Jef Poskanzer.