title: OpenCV 3 OpenCL UMat drawing functions
body: <p>I'm upgrading to OpenCV 3 and using the UMat T_API OpenCL container instead of Mat. </p>
  
  <p>It appears that drawing functions like rectangle(Mat img, ...) don't have a UMat overload. I would like to work in the UMat world as much as possible for drawing on frames without having to convert UMat back to Mat for drawing and displaying. </p>
  
  <p>Can anyone give me the most efficient way to draw a rectangle on a UMat? Or do I have to convert back to Mat to draw on and display?</p>