ppmchange
Change all pixels of one color in a PPM image to another color.
TLDR
Exchange the first color in each oldcolor - newcolor pair with the second color
$ ppmchange [oldcolor1 newcolor1 oldcolor2 newcolor2 ...] [path/to/input.ppm] > [path/to/output.ppm]
Specify how similar colors must be in order to be considered the same
$ ppmchange -closeness [percentage] [oldcolor1 newcolor1 oldcolor2 newcolor2 ...] [path/to/input.ppm] > [path/to/output.ppm]
Replace all pixels not specified in the arguments by a color
$ ppmchange -remainder [color] [oldcolor1 newcolor1 oldcolor2 newcolor2 ...] [path/to/input.ppm] > [path/to/output.ppm]
