/*
第一行图片:
Portrait (ios 12+) : iPhone XS Max 1242*2688 iPhone XR 828*1792
Landscape (ios 12+): iPhone XS Max 2688*1242 iPhone XR 1792*828
第二行图片:
Portrait (ios 11+) : iPhone X/iPhone XS 1125*2436
Landscape (ios 11+): iPhone X/iPhone XS 2436*1125
第三行图片:
iPhone Portrait (ios 8+) : Retina HD 5.5 1242*2208 Retina HD 4.7 750*1334
iPhone Landscape (ios 8+): Retina HD 5.5 2208*1242
第四行图片:
iPhone Portrait (ios 7+) : 2x 640*960 Retina 4 640*1336
第五行图片:
iPhone Portrait (ios 5,6): 1x 320*480 2x 640*960 Retina 4 640*1336
*/总共需要的尺寸
