This is a proof-of-concept fast PNG encoder that uses AVX2 and a special Huffman table to encode images faster. Speed on a single core is anywhere from 180 to 800 MP/s on a Threadripper 3970x, depending on compile time settings and content.
It supports 8 and 16 bit content, 1 to 4 channels; it can also emit cICP chunks for signaling that the content should be interpreted as HDR.