https://github.com/DarthSim/imgproxy/ imgproxy I've not seen mentioned, it is probably the fastest image processing I've used yet. It uses libvips, https://github.com/jcupitt/libvips/wiki/HOWTO----Image-shrin... which not only handles resizing & other basic img needs but optimizes on top of being very light weight on memory & CPU cycles compared to most other implementations.