title: Compare similar images using OpenCV feature matching
body: <p>I am a new in OpenCV. Currently, I want to write the demo using OpenCV feature matching to find all the similar images from the set of images.
  Firstly, I want to try to compare two images first. And I use this code to do:
  <a href="https://stackoverflow.com/questions/16647129/opencv-creating-a-match-of-features-meaning-of-output-array-java">openCV: creating a match of features, meaning of output array, java</a>
  So I tested this code by input two similar images but has one is the rotation. And then I try to input two totally different images such as lena.jpeg vs car.png (any car).</p>
  
  <p>I see that the algorithm still return <strong>matches</strong> matrix between two those different images. </p>
  
  <p>My question here is how can I point that one case is similar image and  one case is not after I got this matrix: 
  flannDescriptorMatcher.match(descriptor1,
      descriptor2, matches.get(0));
  because I don't want to draw matching point between two images, I want factor to distinguish those case.</p>
  
  <p>Thank!</p>