title: Using method convertTo in opencv java wrapper
body: <p>any body please help me to understand how to use method convertTo in JavaCV. i was trying and searching a lot of time and not find the proper answer. <strong>so my problem is</strong>, when i try to convert type of mat from gray image to CV_32F and try to display it in android screen it will give me no result. this my source : </p>
  
  <pre><code>    Imgproc.cvtColor(src, dst, Imgproc.COLOR_RGBA2GRAY, 1); // dst is gray image
      dst.convertTo(dst_f, CvType.CV_32F, 1./255, 0); //convert dst to CV_32F with optional scale
      Imgproc.cvtColor(dst_f, src, Imgproc.COLOR_GRAY2RGBA, 4); // to display it in android before convert to bitmap
  </code></pre>
  
  <p>I was trying also in opencv C++ with this code and it run smoothly : </p>
  
  <pre><code>    imshow("dst", image);
      cvtColor(image, dst, CV_BGR2GRAY);
      dst.convertTo(dst_f, CV_32F, 1.0/255, 0);
      imshow("dst_f", dst_f);
  </code></pre>
  
  <p><strong>UPDATED :</strong></p>
  
  <p>I think i wrong when i try to display image online in android screen. i don't know how to display it altough i knew that android need 4 channel to display image in screen. but when i convert gray to CV_32F image type and i try to display with same code like above and it run smoothly without <strong>no result.</strong></p>