title: Calculate distance between two descriptors
body: <p>I'm trying to calculate the distance (Euclidean or hamming) between two descriptors already calculated. The problem is I don't want to use a matcher, I just want to calculate the distance between two descriptors.
  I'm using OpenCV 2.4.9 and i have mine descriptors stored in a Mat type:</p>
  
  <pre><code>Mat descriptors1;
  Mat descriptors2; 
  </code></pre>
  
  <p>and now i just want to calculate the distance (preferably the Hamming distance since I'm using binary descriptors) between row1 of descriptors1 and row1 of descriptors2 (for example).</p>
  
  <p>I have tried to use bitwise_xor() function but then I got not an effective way of doing the bitcount. There is no function to calculate the hamming distance between two arrays?</p>
  
  <p>I notice that I'm fairly new to OpenCV but I appreciate any help. Thank you</p>