The interesting part about PNG is that since it uses the DEFLATE algorithm, and only applies compression per row/line, with no awareness of relationships between lines, is that in most cases, the effective compression is nearly the same as if you took apart each row of uncompressed pixels as an individual image, and took all those separate images and put them in a zip file.<p>Disregarding the cruft of headers and other file format overhead, there would be a direct relationship between the size of a PNG image, and the raw, uncompressed row-level data zipped up and handled in a similar way.