title: How to remove black part from the image?
body: <p>I have stitched two images together using OpenCV functions and C++. Now I am facing a problem that the final image contains a large black part. </p>
  
  <p>The final image should be a rectangle containing the effective part. 
  My image is the following:</p>
  
  <p><img src="https://i.stack.imgur.com/9UVjk.jpg" alt="enter image description here"></p>
  
  <p>How can I remove the black section?</p>