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 every-
    where 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 con-
    vert 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 num-
    ber: #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)