Produce mask of areas of a certain color in a ppm file
ppmcolormask color [ppmfile]
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:
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An X11-style color name (e.g. black).
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An X11-style hexadecimal specifier: rgb:r/g/b, where r g and b are each 1- to 4-digit hexadecimal numbers.
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An X11-style decimal specifier: rgbi:r/g/b, where r g and b are floating point numbers between 0 and 1.
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For backwards compatibility, an old-X11-style hexadecimal number: #rgb, #rrggbb, #rrrgggbbb, or #rrrrggggbbbb.
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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.)
Bryan Henderson ([email protected])