不使用UIImagePickerControllerOriginalImage获取相册图片

一般用imagePickerController获取到dic以后常用的方法是使用

UIImage *image = [dic objectForKey:@"UIImagePickerControllerOriginalImage"];

来获取原图，但是我使用这个方法获取到得图片并不是原图，而是尺寸经过压缩后的，后来找到了一个新的方法来进行获取 直接贴代码

       ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
            [library assetForURL:[dic objectForKey:UIImagePickerControllerReferenceURL]
                     resultBlock:^(ALAsset *asset)
             {
                 ALAssetRepresentation *representation = [asset defaultRepresentation];
                 CGImageRef imgRef = [representation fullResolutionImage];
                 UIImage *image = [UIImage imageWithCGImage:imgRef
                                                    scale:representation.scale
                                              orientation:(UIImageOrientation)representation.orientation];
                 NSData * data = UIImageJPEGRepresentation(image, 0.5);                

             }failureBlock:^(NSError *error){
                 NSLog(@"couldn't get asset: %@", error);
             }
             ];