title: C++ Unable to detect ellipses on music staff by using SimpleBlobDetection in OpenCV
body: <p>I want to detect circles/ellipses on a music staff by using SimpleBlobDetection but when I try to detect them, it finds unrelated points on picture. </p>
  
  <p>Original Image:</p>
  
  <p><img src="https://i.stack.imgur.com/s6hk5.png" alt="enter image description here"></p>
  
  <p>After Blob Detection:</p>
  
  <p><img src="https://i.stack.imgur.com/qGrAp.jpg" alt="enter image description here"></p>
  
  <p>Please see the code in below:</p>
  
  <pre><code>cv::SimpleBlobDetector::Params params;
  
  //Thresholds
  params.minThreshold = 10;
  params.maxThreshold = 200;
  
  // Filter by Area
  params.filterByArea = true;
  params.minArea = 100;
  params.maxArea = 500;
  
  // Filter by Circularity
  params.filterByCircularity = true;
  params.minCircularity = 0.1;
  params.maxCircularity = 0.5;
  
  // Filter by Convexity
  params.filterByConvexity = true;
  params.minConvexity = 0.57;
  params.maxConvexity = 0.97;
  
  // Filter by Inertia
  params.filterByInertia = true;
  params.minInertiaRatio = 0.01;
  
  // set up and create the detector using the parameters
  cv::SimpleBlobDetector blob_detector(params);
  
  // detect!
  vector&lt;cv::KeyPoint&gt; keypoints;
  blob_detector.detect(tresh, keypoints);
  
  // extract the x y coordinates of the keypoints: 
  for (int i = 0; i &lt; keypoints.size(); i++){
      float X = keypoints[i].pt.x;
      float Y = keypoints[i].pt.y;
      circle(tresh, Point(X, Y), 1, Scalar(0, 255, 0), 3, CV_AA);
  }
  
  imshow("Detected Blobs", tresh);
  </code></pre>
  
  <p>Help me please...</p>