I have some images that are very noisy, but the values are all in a narrow range of near-zero uint8 values. I think Huffman coding might be optimal for compressing them, since there is a lot of bit-wise redundancy but not a lot of sequence redundancy. However I can’t find any image formats that use the plain bit-wise algorithm without encoding sequences (like PNG or Deflate do). The closest I found was an obsolete Unix command line tool called “pack”. Is there an image format that uses plain old Huffman compression?