Thanks, @Thev00d00, I hadn't herd of this! I've amazed folks in the past with things I've built to do fairly heavy duty image processing using only shell (incl. Unix text utilities and awk) and ImageMagick, even though I am not a programmer!

I almost didn't click through to read about libvips, since I only want to use these tools from a CLI/shell interface, but - would you look at that - it's got command line bindings! I'm going to have to give this a try to see if it can do some of the "magick" stuff...