问题
During testing i found some thing strange in Xcode. I have a png of size 2.2 mb and the png compression is "YES" in the build setting after archive i extract the build and found that Xcode converted the png to 3.8 mb. Then with same test and png compression is "NO" in build settings then the image have same size of 2.2 mb. Is Xcode extend the size of PNG afte compression ??
回答1:
In all of my own apps, I keep PNG compression set to OFF as Apple has traditionally had problems dealing with compressed app icons (in PNG format) not being recognized during the app store submission process.
And since you're seeing pretty wretched PNG compression for your own app, you might as well keep PNG compression set to disabled.
PNG compress may be useful for apps that have a LOT of PNG graphics (especially larger PNG files) built into it.
来源：https://stackoverflow.com/questions/13524058/xcode-png-compression-issue