title: Arrow in specific direction
body: <p>I am trying to implement arrow formation at the ends of the video frame that i have to show the direction of the moving vehicles. I have no idea how to proceed. Do I have to use Frame Subtraction method. I am confused. I can't even upload the sample photo to show the output.</p>
  
  <p>I am unable to find solution. Please help me out.
  I have black and white background. I need to plot arrows in the black region. I am helpless.</p>