What are some good resources to learn high performance image processing?
For context, I am interested in building a photo editor on the web.
Most libraries that you will use will probably use ImageMagick. I'd suggest looking into those depending on your language of choice and also see what ImageMagick in general can do:
https://imagemagick.org/index.php
Im a fan of lovell's sharp (just google "github lovell sharp" lol) which is on some ways more performant than other libraries because it uses libvips