title: Prominent lines not detected by Hough Transform
body: <p>After running Canny edge detector on an image i'm getting clear lines. But the Hough line function seems to be missing out on pretty prominent lines when run on the Canny edgemap image.
   I'm keeping only vertical and horizontal Hough lines (a tolerance of 15 degrees). Lots of extra lines are coming up but clearly visible lines bounding the rectangles are not being picked up.</p>
  
  <p>Here's the snippet:</p>
  
  <pre><code>cvCanny( img, canny, 0, 100, 3 );
  lines = cvHoughLines2( canny, storage, CV_HOUGH_PROBABILISTIC, 1, CV_PI/180, 35, 20, 10 );
  </code></pre>
  
  <p>The main intention is to detect the rectangular boxes that denote the nodes of the linked list. However the squares.c sample program will detect only perfect rectangles, not if an arrowhead is touching the rectangle boundary.</p>
  
  <p>Could you please explain the sort of changes to Hough line function which will help me get hough lines corresponding to clearly visible lines in Canny edge image?</p>
  
  <p><img src="https://i.stack.imgur.com/FSvMp.png" alt="hough"></p>