I seem to be having issues replicating the iOS png optimizations that xcode makes. Our app allows users to update content via an asset server by comparing the checksums of the files stored in the bundle with those on the server. Before any pngs are uploaded to the server they are subjected to the iphoneos-optimize script inside the xcode developer directory (Stack Overflow post). The trouble is that the checksum performed (both by the server and the device) on the pngs produce different results.
It is worth mentioning that this is tested on the device and not the simulator (which doesn’t crush the pngs). Also the visible results are the same it is merely the checksum that is different.