ppmdist
Produce a grayscale version of a PPM image.
TLDR
Produce a grayscale version of the specified PPM image
$ ppmdist [path/to/input.ppm] > [path/to/output.pgm]
Specify the method used to map colors to graylevels
$ ppmdist -[frequency|intensity] [path/to/input.ppm] > [path/to/output.pgm]
