ppmdither
Reduce the number of colors in an image by applying dithering.
TLDR
Read a PPM image, apply dithering and save it to a file
$ ppmdither [path/to/image.ppm] > [path/to/file.ppm]
Specify the desired number of shades for each primary color
$ ppmdither -red [2] -green [3] -blue [2] [path/to/image.ppm] > [path/to/file.ppm]
Specify the dimensions of the dithering matrix
$ ppmdither -dim [2] [path/to/image.ppm] > [path/to/file.ppm]
