如何通过ALAssert获取相册原图

1、前提你要确定ALAssert中带的是图片（因为也可能是视频）

[asset valueForProperty:ALAssetPropertyType] == ALAssetTypePhoto

2、获取原图：

- (UIImage *)getImage:(ALAsset *)asset {
     ALAssetRepresentation *representation = [asset defaultRepresentation];
     CGImageRef resolutionRef = [representation fullResolutionImage];
     UIImage *image = [UIImage imageWithCGImage:resolutionRef scale:1.0f orientation:(UIImageOrientation)representation.orientation];
     return image;
}