title: calcOpticalFlowPyrLK horizontal and vertical flow u,v
body: <p>I need to get the u,v components so that I can compute an avoidance strategy of obstacles for blind people.
  I will divide the frame into 2 halves and sum up the flow components u+v in them the avoidance strategy will be that the blind person will move away from the half that has the higher value of flow .</p>
  
  <p>The function calcOpticalFlowPyrLK in opencv returns the position of the points in the new frame however I need the u and v components.
  How can that be achieved. And also is there an avoidance strategy that I can use better than this one using only an RGB camera</p>