In the Pixel Editing category one could probably add the VIPS library (http://www.vips.ecs.soton.ac.uk), which is one of the fastest and less memory-demanding processing libraries in the FOSS market (and the core of my PhotoFlow editor).
VIPS is also used by Sharp, an high performance Node.js module to resize JPEG, PNG, WebP and TIFF images (GitHub - lovell/sharp: High performance Node.js image processing, the fastest module to resize JPEG, PNG, WebP, AVIF and TIFF images. Uses the libvips library.). Maybe this could be interesting for this site as well…