NAME
ppmcolormask - produce mask of areas of a certain color in a PPM file
SYNOPSIS
ppmcolormask color [ppmfile]
DESCRIPTION
Reads a PPM file as input. Produces a PBM (bitmap) file as output.
The output file is the same dimensions as the input file and is black
in all places where the input file is the color color, and white
everywhere else.
The output of ppmcolormask is useful as an alpha mask input to pnmcomp.
Note that you can generate such an alpha mask automatically as you
convert to PNG format with pnmtopng(1). Use its -transparent option.
ppmfile is the input file. If you don’t specify ppmfile, the input is
from Standard Input.
The output goes to Standard Output.
You can specify color five ways:
o An X11-style color name (e.g. black).
o An X11-style hexadecimal specifier: rgb:r/g/b, where r g and b
are each 1- to 4-digit hexadecimal numbers.
o An X11-style decimal specifier: rgbi:r/g/b, where r g and b are
floating point numbers between 0 and 1.
o For backwards compatibility, an old-X11-style hexadecimal
number: #rgb, #rrggbb, #rrrgggbbb, or #rrrrggggbbbb.
o For backwards compatibility, a triplet of numbers separated by
commas: r,g,b, where r g and b are floating point numbers
between 0 and 1. (This style was added before MIT came up with
the similar rgbi style.)
SEE ALSO
pgmtoppm(1), pnmcomp(1), pbmmask(1), ppm(5)
AUTHOR
Bryan Henderson (bryanh@giraffe-data.com)
14 April 2000 ppmcolormask(1)