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

R pnmcomp . Note that you can generate such an alpha mask automatically as you convert to PNG format with

R 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.

R 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.)


R pgmtoppm (1),

R pnmcomp (1),

R pbmmask (1),

R ppm(5)


Bryan Henderson ( ) \" Contributed to the public domain.