Retina display compatibility

For our iPhone app, we are using 50 x 50 user image (from facebook). It works fine for iPhone 3G开发者_JAVA技巧 and 3GS but not for iPhone 4 due to its high resolution display. For iPhone 4 we tried to send 100 x 100 (variable height) image but it is not working for obvious reasons. Any thought?

You don't need to do anything different for the Retina Display. Using exactly the same image as you have on the older iPhone will work exactly the same.

If you have a higher resolution image that you'd like to display instead, then if you save the file with a @2x suffix then, if the device has a Retina display, it will pick that instead. In most cases it should not require any extra code.