This is pretty neat. A lot like the filtering done in PNG, just without slapping zlib on the result. As far as SIMD goes, I agree with the author and don't see

This is pretty neat. A lot like the filtering done in PNG, just without slapping zlib on the result. As far as SIMD goes, I agree with the author and don't see much potential, as instructions are variable-length and most instructions encode deltas. It's probably quite close to optimal by just letting the CPU figure it out on the micro-level. If each line were encoded independently they could be en- and decoded in parallel (once you add a skip instruction to tell where the next line starts, this does preclude streaming of intra-line output though). The hit to compression ratio should be small as long as images are wide enough for the color buffer reset to not matter.