title: Manually make pairwise matching in OpenCV from features key points
body: <p>Here's my problem. I manually extracted key points features with SURF on multiple images. But I also already know which pair of points are going to match. The thing is, I'm trying to create my matching pairs, but I don't understand how. I tried by looking at the code, but it's a mess.</p>
  
  <p>Right now, I know that the size of the features.descriptors, a matrix, is the same as the number of key points (the other dimension is 1). In the code, to detect matching pairs, it's only using the descriptors, so it's comparing rows (or columns, I'm not sure) or two descriptors matrix and determined if there's anything in common.</p>
  
  <p>But in my case, I already know that there's a match between keypoint i from image 1 and keypoint j from image 2. How do I describe that as a MatchesInfo value. Particularly the element matches of type std::vector&lt; cv::DMatch >.</p>
  
  <p>EDIT: So, for this, I don't need to use any matcher or anything like this. I know which pairs are going together!</p>