This is pretty neat! The compression rates and encode/decode rates are impressive for such a simple rule set. > SIMD acceleration for QOI would also be cool bu

This is pretty neat! The compression rates and encode/decode rates are impressive for such a simple rule set. > SIMD acceleration for QOI would also be cool but (from my very limited knowledge about some SIMD instructions on ARM), the format doesn't seem to be well suited for it. Maybe someone with a bit more experience can shed some light? I don’t know about SIMD encoding, but for decoding at least, the core problem is to make some unit of the image (pixels, scanlines, blocks, etc) independently addressable (readable). The current format is complicated due to pixels of different sizes; there’s no way to know where data for pixel 1000 starts without reading all preceding 999 pixels. You could build a prefix-sum array of pixel indices, but that will fully undermine your compression. One question might be how well does QOI work on independent scan lines or blocks? Is the compression still pretty good if the look-back window is limited in size and restarts every once in a while? To make a GPU capable format, the very first thing you would probably need to do is separate the tag bits from all the other data, so a thread could identify the pixel type by direct lookup into the tag buffer. It then needs to know where to go to find the remaining data, so you’d probably need at least one byte of data that could be used to reliably locate the rest of the data. I don’t see an easy way to make this happen for separate pixels, but it might not be bad if the image is encoded in blocks or scanlines.