title: how to compare size of kepoints matching in opencv
body: <p>I'm going compare images with SURF detector in opencv. for this work,I need size and Orientation of keypoints that must be compare them. for example, I have to extract keypoints matching of second image larger than keypoints matching of first image. (keypoint 1.size > keypoint 2.size).</p>
  
  <p><strong>question:</strong> 
  <strong>how to extract size of keypoints matching  in opencv?</strong> </p>