pamditherbw
Apply dithering to a greyscale image, i.e. turn it into a pattern of black and white pixels that look the same as the original greyscale.
TLDR
Read a PGM image, apply dithering and save it to a file
$ ppmditherbw [path/to/image.pgm] > [path/to/file.pgm]
Use the specified quantization method
$ ppmditherbw -[floyd|fs|atkinson|threshold|hilbert|...] [path/to/image.pgm] > [path/to/file.pgm]
Use the atkinson quantization method and the specified seed for a pseudo-random number generator
$ ppmditherbw -atkinson -randomseed [1337] [path/to/image.pgm] > [path/to/file.pgm]
Specify the thresholding value for quantization methods that perform some sort of thresholding
$ ppmditherbw -[fs|atkinson|thresholding] -value [0.3] [path/to/image.pgm] > [path/to/file.pgm]
