title: OpenCV density of feature points
body: <p>Using OpenCV SIFT algorithm i am able to get the matching and non matching feature points between 2 images. My solution is <a href="https://stackoverflow.com/questions/43775842/opencv-draw-non-matching-points/43782475#43782475">here</a><br>
  The distribution of matched(green) and non-matched(red) feature points is as shown below.(i cant reveal the actual image. but the image contains mostly text)
  <a href="https://i.stack.imgur.com/24dPw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/24dPw.png" alt="enter image description here"></a>
  I want to calculate a density function for the matching and non matching points on an image(i.e. given a nXn area on the image, density function should give how many matching points are present inside this nXn area). How can i do that?
  <br>Secondly, i want to calculate a function that gives ratio of densities of matching and non-matching feature points inside a nXn area on the image.<br>I am using Python code on Windows 7 and build from latest OpenCV source.</p>