);         Converters.Mat_to_vector_Mat(pyramid_mat, pyramid);         return retVal;     }  /**  * <p>Constructs the image pyramid which can be passed to "calcOpticalFlowPyrLK".</p>  *  * @param img 0-bit input image.  * @param pyramid output pyramid.  * @param winSize window size of optical flow algorithm. Must be not less than  * <code>winSize</code> argument of "calcOpticalFlowPyrLK". It is needed to  * calculate required padding for pyramid levels.  * @param maxLevel 0-based maximal pyramid level number.  *  * @see <a href="http://docs.opencv.org/modules/video/doc/motion_analysis_and_object_tracking.html#buildopticalflowpyramid">org.opencv.video.Video.buildOpticalFlowPyramid</a>  */     public static int buildOpticalFlowPyramid(Mat img, List<Mat> pyramid, Size winSize, int maxLevel)     {         Mat pyramid_mat = new Mat();         int retVal = buildOpticalFlowPyramid_0(img.nativeObj, pyramid_mat.nativeObj, winSize.width, winSize.height, maxLevel);         Converters.Mat_to_vector_Mat(pyramid_mat, pyramid);         return retVal;     }       //     // C++:  double calcGlobalOrientation(Mat orientation, Mat mask, Mat mhi, double timestamp, double duration)     //  /**  * <p>