Using PNG Predictors to Enhance GZIP/PKZIP/FLATE Compression

While implementing Binary Cross Reference Streams we were surprised to see that they could be encoded with PNG Predictors. This was surprising because binary cross reference streams aren’t images, they are byte tables. The first byte can only contain the numbers 0, 1 and 2 and are often the same, the middle two bytes are often the same and the last byte is generally increasing by one each time. Knowing this about the data you can develop a lossless algorithm which normalizes the data and so makes PKZIP/GZIP/FLATE compression work much better.