title: Using OpenCV fitEllipse() for circle fitting
body: <p>Is it valid to use OpenCV <a href="http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html?highlight=fitellipse#cv2.fitEllipse" rel="noreferrer">fitEllipse</a> for circle fitting. 
  fitEllipse() returns <code>cv::RotatedRect</code> how about averaging width and height to get fitted circle radius?</p>