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 hex­
              adecimal  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)


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