title: OpenCV - After feature points detection, how can I get the x,y-coordinates of the feature points
body: <p>My process is </p>
  
  <ul>
  <li>first is to detect the feature points</li>
  <li>next, I want the x,y-coordinates of feature points in order to build a histogram to find the local density of maxima of x,y histogram</li>
  </ul>
  
  <p>Any helps is appreciate</p>
  
  <p>Following this example: <a href="http://docs.opencv.org/3.0-beta/doc/py_tutorials/py_feature2d/py_orb/py_orb.html#orb" rel="nofollow">http://docs.opencv.org/3.0-beta/doc/py_tutorials/py_feature2d/py_orb/py_orb.html#orb</a></p>