#import <AssetsLibrary/AssetsLibrary.h>

//UserCenter 是一個單例，library是UserCenter的ALAssetsLibrary類的屬性。

[UserCenter center].library = [[ALAssetsLibrary alloc] init];

//取高清圖片仔細看下面方法

+ (void)analyticalRetinaImageWithPhoto:(PhotoAsset *)phAsset completeBlock:(void (^)(UIImage *image))block;
{
    [[UserCenter center].library assetForURL:phAsset.asset.defaultRepresentation.url resultBlock:^(ALAsset *asset)  {
        // 取正確方向的高清圖片
        CGImageRef ref = asset.defaultRepresentation.fullResolutionImage;
        CGFloat scale = asset.defaultRepresentation.scale;
        UIImageOrientation orientation = (UIImageOrientation)asset.defaultRepresentation.orientation;
        UIImage *tempImg = [UIImage imageWithCGImage:ref scale:scale orientation:orientation];
        block(tempImg);
        // 取高圖片，但方向可能不正確
//      UIImage *tempImg = [UIImage imageWithCGImage:asset.defaultRepresentation.fullResolutionImage];
//      block(tempImg);
    }failureBlock:^(NSError *error) {}];
}