I'm not knowledgeable to speak to that, but just to clarify—the low-hanging fruit in libpng I mentioned is in simple, vectorizable loops—conversions between pix

I'm not knowledgeable to speak to that, but just to clarify—the low-hanging fruit in libpng I mentioned is in simple, vectorizable loops—conversions between pixel formats in buffers. Not in its compression algorithm (which isn't part of libpng—it calls out to zlib for that).