JPEG-XL's lossless mode has something called the "squeeze transform" which operates over the image data in 2D. It's a variation of the Haar Transform, which wor

JPEG-XL's lossless mode has something called the "squeeze transform" which operates over the image data in 2D. It's a variation of the Haar Transform, which works on a similar principle as DCT https://en.wikipedia.org/wiki/Haar_wavelet#Haar_transform https://en.wikipedia.org/wiki/Haar_wavelet#Haar_transform It also has "meta-adaptive filters", which act similarly to PNG's filters except you get to encode a custom decision-tree that defines how pixels are filtered, as a function of their neighboring pixels