title: Find a similar contour in a dark image
body: <p>I am searching a way to detect a specific contour (boundary) in this picture:
  <a href="https://i.stack.imgur.com/cyuqb.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cyuqb.jpg" alt="enter image description here"></a></p>
  
  <p>I have already detected a similar contour (drawn in red) and would like detect the closest contour.
  <a href="https://i.stack.imgur.com/ubhb3.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ubhb3.jpg" alt="enter image description here"></a></p>
  
  <p>The red contour is almost the same; just a litle smaller.</p>
  
  <p>I try with cv::SimpleBlobDetector but it is not possible to help the detection with passing a similar contour.I try with an area filter but is not conclusive.</p>
  
  <p>Do you have an idea?</p>
  
  <p>Thanks in advance</p>