title: Open CV addWeighted Error
body: <p>Hi i am trying to draw some transparent shapes over a webcam feed.</p>
  
  <p>I am encountering the error Sizes of Input argument do not matched. I have check my code and could not identify the fault</p>
  
  <pre><code>    double alpha = 0.8;
      Mat polarize(480, 640, CV_8UC4);
  
      Size s = webcam.size();
      double rows = s.height;
      double cols = s.width;
      std::cout &lt;&lt; "Webcam R " &lt;&lt; rows &lt;&lt; "   C " &lt;&lt; cols &lt;&lt; std::endl;
  
      s = shape.size();
      rows = s.height;
      cols = s.width;
  
      std::cout &lt;&lt; "Shape R " &lt;&lt; rows &lt;&lt; "   C " &lt;&lt; cols &lt;&lt; std::endl;
  
  
      addWeighted(shape, alpha, webcam, 1.0 - alpha, 0.0, polarize); // Error Here
  </code></pre>
  
  <p>I have checked that both Mat shape and Mat webcam is of the same Row and Column. Is there any thing that i missed ?</p>