title: How to read UMat from a file in opencv 3.0 Beta?
body: <p>I want to use <code>UMat</code> so my code can be run on both GPU and CPU using OpenCL (OpenCV 3.0.0 Beta).</p>
  
  <p>but I can not find a way to read an image file into a <code>UMat</code> or convert a <code>Mat</code> to <code>UMat</code>. </p>
  
  <p>How can I read an image into a <code>UMat</code>?</p>