ppmtopcx
Convert a PPM image to a PCX file.
TLDR
Convert a PPM image to a PCX file
$ ppmtopcx [path/to/file.ppm] > [path/to/file.pcx]
Produce a PCX file with the specified color depth
$ ppmtopcx -[8bit|24bit] [path/to/file.ppm] > [path/to/file.pcx]