Upon submission of an iPhone app to iTunes Connect for AppStore distribution, they ask for a 512x512 pixel image. Here is what it says next to the place to submit it:
"A large version of your app icon that will be used on the App Store. It must be at least 72 DPI and a minimum of 512x512 pixels (it cannot be scaled up). It must be flat artwork without rounded corners."
So are they going to round the corners like they do elsewhere or not?? The iOS Human Interface Guidelines indicate NOT: "There are no visual effects added to this version of your application icon"
Yet all the images I see on iTunes app store are rounded. Also web version of iTunes show rounded icons, and infact are 175, 175 square with an image mask that has rounded corners: http://a1.phobos.apple.com/us/r1000/050/Purple/49/68/e3/mzi.wijnmlbw.175x175-75.jpg and http://ax.phobos.apple.com.edgesuite.net/htmlResources/2CBF/images/mask175.png.
Your intuition is correct - Apple applies the glossiness and rounded corners automatically in the iTunes Store, so just upload a flat square version.
Don't worry if the rendering looks terrible in iTunes Connect - it will be fine once it's on the store.
The iOS Guidelines appear to be incorrect.
Apple will indeed round the corners of the flat artwork uploaded to iTunes Connect. It will also add a gloss automatically. So you can upload just the square flat version, but an already rounded version will also work just fine.
If your icon already includes gloss, you can add the UIPrerenderedIcon key to your Info.plist. If you use the build in plist editor of Xcode, the full name of the key is Icon already includes gloss effects and you must set it to YES. iTunes Connect will honour the settings in that file and will update the preview of your uploaded artwork after you upload your binary.
Important: Make sure the UIPrerenderedIcon key is in the root of your Info.plist, otherwise the icon uploaded to iTunes Connect will still use the default gloss, because it will not recognize this key.
来源：https://stackoverflow.com/questions/4580978/512x512-image-for-appstore-itunes-connect-will-apple-do-corner-rounding-like