Basically. There are three ways to losslessly compress a JPEG: 1) Huffman table optimization 2) Ordinary progressive scan 3) Trying all sorts of split order

Basically. There are three ways to losslessly compress a JPEG: 1) Huffman table optimization 2) Ordinary progressive scan 3) Trying all sorts of split orders for progressive scan Most image apps worth their salt hopefully do 1) and 2). This script does 1) if it wasn't done already, and 3), which is its main purpose.