title: Detect corner points on text with Opencv
body: <p>I need a help on image processing on opencv, I have a kind of trapez to process, so I need to warp Perspective, it´s easy to do this, but I need extract source points on this image.
  Note, the image has only a text, on this example I draw red lines to show what I need to get.  I need detect the corner points (marked with a blue point on example).</p>
  
  <p><img src="https://i.stack.imgur.com/vR6tZ.png" alt="enter image description here"></p>
  
  <p>Any help?</p>