title: How can only detect the white borders in this image using python and openCV
body: <p><a href="https://i.stack.imgur.com/f1sHX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/f1sHX.jpg" alt="tennis court"></a></p>
  
  <p>How can I detect the white lines alone from the above image using opencv python?
  which method can I use? or is there any inbuilt function available for this purpose?  </p>
  
  <p>Hough's didn't work well on this case.
  The final output should like these:
  <a href="https://i.stack.imgur.com/5Q4R2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5Q4R2.png" alt="lane"></a> <a href="https://i.stack.imgur.com/3YzRz.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3YzRz.jpg" alt="enter image description here"></a></p>