ppmcolormask - 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:

   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.)


   pgmtoppm(1), pnmcomp(1), pbmmask(1), ppm(5)


   Bryan Henderson (bryanh@giraffe-data.com)

                             14 April 2000                 ppmcolormask(1)


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