UIImage将图片写入本地相册
UIImageWriteToSavedPhotosAlbum(<#UIImage *image#>, <#id completionTarget#>, <#SEL completionSelector#>, <#void *contextInfo#>)
例子:
UIImage *image = [UIImage imageNamed:@"yintingting"];
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);