[Zlib-devel] Google's version of zlib code

[glennrp at comcast.net]

I split my test suite into groups by size, and added
the 24 Kodak test images, to see if the results were
dependent on image size.  Not much, except for the
very small ones:

    Size range    pngcrush   zopfli    z/pc
    0-200            11818    11618   .9831
    201-1000        140290   136015   .9695
    1001-10000     1040052  1000877   .9623
    10001-200000   2756452  2568988   .9320
    300000-450000   332611   318047   .9562
    450001-999999 15246402 14717411   .9653

If you were to consider the chunk overhead and PNG signature
bytes that appear in each file (a minimum of 61 bytes), the
zopfli/pngcrush ratio for the very small ones would be much closer
to 1.0.  There are 379 files in that (0-200) group, so the
reduction due to zopfli is about half a byte per file.

Glenn