That's also my feeling -- the CLI tooling with imagemagick or various image libraries in various programming languages are quite good. For instance, with ipytho

That's also my feeling -- the CLI tooling with imagemagick or various image libraries in various programming languages are quite good. For instance, with ipython, numpy and OpenCV I can edit images in a REPL fashion without even thinking about image file formats. Anyway, if you like PPM, you may also like https://tools.suckless.org/farbfeld/ https://tools.suckless.org/farbfeld/ . The guys from suckless picked up the unix philosophy for simple file formats and pipes, cf. the examples https://tools.suckless.org/farbfeld/examples/ https://tools.suckless.org/farbfeld/examples/