iPhone分辨率
1.iPhone 5 - 1136 X 640 -> 568 X 320
2.iPhone 4/4S - 960 X 640 -> 480 X 320
3.iPhone ./3G/3GS - 480 X 320 -> 480 X 320
1.iPhone 5 - 1136 X 640 -> 568 X 320
2.iPhone 4/4S - 960 X 640 -> 480 X 320
3.iPhone ./3G/3GS - 480 X 320 -> 480 X 320