title: goodFeaturesToTrack gives zero size vector
body: <p>I am trying to use the <code>goodFeatureToTrack()</code> function with opencv 2.4.3 on an gray image of lena...however I always get a zero size of the vector storing the features as <code>cv::Point2f</code>...I have tried using a zero mask also but in that case the application hangs up..I tried playing with the quality level value from 0.01 to 0.001. However still the size of the vector is zero..any idea?...following is my code..</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;opencv2/core/core.hpp&gt;
  #include &lt;opencv2/features2d/features2d.hpp&gt;
  #include &lt;opencv2/video/tracking.hpp&gt;
  #include &lt;opencv2/highgui/highgui.hpp&gt;
  #include &lt;vector&gt;
  
  using namespace cv;
  using namespace std;
  
  int main()
  {
      Mat frameROI;
      frameROI = imread("C:\\lena.jpg");
      std::vector&lt;cv::Point2f&gt; corners;
      cvtColor(frameROI,frameROI,CV_RGB2GRAY);
  
      //Mat mask(frameROI.size(), CV_8UC1);
      //mask.setTo(Scalar::all(0));
  
      //goodFeaturesToTrack(frameROI,corners,10,0.001,10,mask,3,false,0.04);
      goodFeaturesToTrack(frameROI,corners,10,0.001,10);//AFTER EDIT
      cout&lt;&lt;"SIZE OF FEATURE VECTOR = "&lt;&lt;corners.size()&lt;&lt;endl;
  
      imshow("VIDEO ROI",frameROI);
      waitKey();
  
      return 0;
  }
  </code></pre>
  
  <p>OUTPUT:</p>
  
  <pre><code>SIZE OF FEATURE VECTOR = 0
  </code></pre>
  
  <p><strong>EDIT:</strong> afte Bob's suggestion I omitted the line for mask and modified the function..but now the application hangs up after the goodFeaturesToTrack function is invoked...Any idea?</p>