Micro Wavelet: done

So I’ve finally implemented NeXT Micro Wavelet decoder (and updated git bundles on the site while at it) and the codec turned out to be even more interesting than on the first glance. The codec itself consists of three distinct phases: using delta prediction along with wavelet transform, packing results into 16-bit opcodes, and further packing the opcodes with Huffman or LZSS compression. There’s also a raw mode which simply transmits 8-bit deltas so it’s not particularly interesting. First stage is probably where the codec name comes from: it works on 2×2 pixel blocks that get transformed into the difference from the previous block means (for each component) plus vertical and horizontal differences between block pixels (the same pair is used for all block components). In other words, not exactly full wavelet transform but not exactly no wavelet transform either. Then the deltas get quantised to a small set of pre-defined values (13 values for red and blue, 15 values for green, 5…