pngdefry is a command line tool for undoing Apple's pngcrush optimizations of png's. On a Mac you can do this with the pngcrush embedded in Xcode, but on any other platform you're shit out of luck. This repository is a fork of Jongware's pngdefry that adds proper compression of the output png, as well as a flag for overriding the default compression level. The original source code can be found here: http://www.jongware.com/pngdefry.html
The original pngdefry created png's at about 50% of the uncompressed image size. For a full screen iPad Retina png that is about 6mb. With proper compression this should be reduced to about 1.5-2mb, depending on your content.
To compile it, run
make
from the command line
If you want to install it to /usr/local run
make install