title: How can I use BruteForce Matching in openCV 3.2.0?
body: <p>I'm using opencv 3.2.0 and I'm trying to feature detecting, descriptor computing, and descriptor matching with FAST, BRISK, BruteForce, respectively. I'm using C++ with Visual studio 2017.</p>
  
  <pre><code>std::vector&lt;KeyPoint&gt; keypoints1, keypoints2;
  cv::Mat descriptors1, descriptors2;
  m_image_A = imread("a.bmp", IMREAD_GRAYSCALE);
  m_image_B = imread("b.bmp", IMREAD_GRAYSCALE);
  cv::Ptr&lt;cv::FeatureDetector&gt; a = cv::FastFeatureDetector::create();
  a-&gt;detect(m_image_A, keypoints1);
  a-&gt;detect(m_image_B, keypoints2);
  cv::Ptr&lt;cv::DescriptorExtractor&gt; ex = cv::BRISK::create();
  ex-&gt;compute(m_image_A, keypoints1, descriptors1);
  ex-&gt;compute(m_image_B, keypoints2, descriptors2);
  
  cv::Ptr&lt;cv::DescriptorMatcher&gt; matcher;
  std::vector&lt;vector&lt;DMatch&gt;&gt; matches;
  
  matcher = cv::BFMatcher::create();
  matcher-&gt;knnMatch(descriptors1, descriptors2, matches, 2);
  </code></pre>
  
  <p>Here's my simple code for this and it doesn't operates properly.
  I read many codes and tips, but I cannot find proper solution for my problem.</p>
  
  <p>Is there anyone who can help me? How can I make it operate properly?</p>