title: Detecting Hough circles android
body: <p>I am trying to detect circles using android. I succeeded to implement the detect lines algorithm but nothing gets displayed when trying the draw hough circles algoritm.</p>
  
  <p><strong>Here is my code:</strong></p>
  
  <pre><code>Mat thresholdImage = new Mat(getFrameHeight() + getFrameHeight() / 2, getFrameWidth(), CvType.CV_8UC1);
              mYuv.put(0, 0, data);
              Imgproc.cvtColor(mYuv, destination, Imgproc.COLOR_YUV420sp2RGB, 4);
              Imgproc.cvtColor(destination, thresholdImage, Imgproc.COLOR_RGB2GRAY, 4);
              Imgproc.GaussianBlur(thresholdImage, thresholdImage, new Size(9, 9), 2, 2 );
  
          Mat circles = new Mat();
  
  
          Imgproc.HoughCircles(thresholdImage, circles, Imgproc.CV_HOUGH_GRADIENT, 1d, (double)thresholdImage.height()/70, 200d, 100d);
  
          Log.w("circles", circles.cols()+"");
          for (int x = 0; x &lt; circles.cols(); x++) 
          {
                  double vCircle[]=circles.get(0,x);
  
                  Point center=new Point(Math.round(vCircle[0]), Math.round(vCircle[1]));
                  int radius = (int)Math.round(vCircle[2]);
                  // draw the circle center
                  Core.circle(destination, center, 3,new Scalar(0,255,0), -1, 8, 0 );
                  // draw the circle outline
                  Core.circle( destination, center, radius, new Scalar(0,0,255), 3, 8, 0 );
  
          }
  </code></pre>