a small qoi enhancement study
Downloaded a sample of 50 random photos from https://source.unsplash.com/random and made some histograms and scatterplots to see if I could see if the QOI_OP_LUMA and QOI_OP_DIFF photo compression ideas of https://github.com/phoboslab/qoi/blob/experimental/qoi.h could be usefully improved.
Octave code for creating plots is included. The histograms and scatterplots produced are after throwing out identical runs.