图标大小
iTunes Artwork icon ───────────────────────── 512px (90px)
App icon(iPhone4) ────────────────────────── 114px (20px)
App icon(iPad) ───────────────────────────── 72px (12px)
App icon(iPhone 3G/3GS) ───────────────────── 57px(10px)
Spotlight/Settings icon icon(iPhone4) ───────────── 58px (10px)
Spotlight/Settings icon icon(iPhone 3G/3GS/iPad) ──── 29px (9px)