title: How to draw matches in Opencv?
body: <p>I have matched two vectors of descriptors of two images:</p>
  
  <pre><code>cv::Ptr&lt;BinaryDescriptorMatcher&gt; bdm = BinaryDescriptorMatcher::createBinaryDescriptorMatcher();
  std::vector&lt;std::vector&lt;cv::DMatch&gt; &gt;  matches;
  float maxDist = 10.0;
  bdm-&gt;radiusMatch(descr2, descr1, matches, maxDist);
  // descr1 from image1, descr2 from image2
  std::vector&lt;char&gt; mask(matches.size(), 1);
  </code></pre>
  
  <p>But now I want to draw the found matches from the two images.</p>
  
  <p>This does not work:</p>
  
  <pre><code>drawMatches(gmlimg, keylines, walls, keylines1, matches, outImg, cv::Scalar::all(-1), cv::Scalar::all(-1), mask, DrawLinesMatchesFlags::DEFAULT);
  </code></pre>
  
  <p>And this neither:</p>
  
  <pre><code>drawLineMatches(gmlimg, keylines, walls, keylines1, matches, outImg, cv::Scalar::all(-1), cv::Scalar::all(-1), mask, DrawLinesMatchesFlags::DEFAULT);
  </code></pre>