Recompress PNGs

Created by: rbrito

Hi there.

While I was testing my page with http://developers.google.com/speed/pagespeed/insights/ the tool told me:

Optimize images Properly formatting and compressing images can save many bytes of data. Optimize the following images to reduce their size by 1.1KiB (44% reduction).

Losslessly compressing http://cdn.mathjax.org/mathjax/2.3-latest/images/CloseX-31.png could save 1.1KiB (44% reduction).

It seems that this problem is reocurring, given issue #734 (closed), for instance. The savings of about 44% sound great, but I guess that Google is being conservative here:

$ optipng -o7 CloseX-31.png 
(...)
Selecting parameters:
  zc = 9  zm = 8  zs = 1  f = 0     IDAT size = 1194

Output IDAT size = 1194 bytes (1328 bytes decrease)
Output file size = 1449 bytes (1196 bytes = 45.22% decrease)

$ advpng -z3 CloseX-31.png 
        1449        1312  90% CloseX-31.png
        1449        1312  90%
$ advpng -z4 -i 10 CloseX-31.png 
        1312        1269  96% CloseX-31.png
        1312        1269  96%

In other words, I obtained a file with total size 1268, which, compared to the original, represents about 48%, considerably more than what Google suggests.

Anyway, even if we don't go after every last saved bit, it would be nice to have a smaller image. If patches are needed, desired, please let me know.

Thanks,

Rogério.