APP图标和启动页尺寸（Icon and Image Sizes）

For iPhone 6:

• 750 x 1334 (@2x) for portrait

• 1334 x 750 (@2x) for landscape

For iPhone 6 Plus:

• 1242 x 2208 (@3x) for portrait

• 2208 x 1242 (@3x) for landscape

官方说明链接：/library/prerelease/ios/documentation/UserExperience/Conceptual/MobileHIG/#//apple_ref/doc/uid/TP40006556-CH27-SW1