title: recognizing rectangular area in an image
body: <p>This sounds like simple thing to do but I am having many issues with it.</p>
  
  <p>By Hough transformation, I think I can get the ROI from the image. But because of our 3D world and my imperfect hand coordination, the ROI is skew, or has perspective projection - that is, it is not a real rectangle for further analysis.</p>
  
  <p>Is there any way to resolve this problem?</p>