Tootfinder

netpbm tools are a suite of tools to convert and fiddle with the ppm/pbm/pgm (collectively pnm) file formats, which are pretty much the simplest image formats on the planet, which even have an ASCII version; so if you have a simple script you want to generate simple images with they're a good choice of format, and if you have them, the pbm tools can convert to/from pretty much anything else or do simple scale/etc - lighter than ImageMagick say.