title: Calibrate trapezoidal distortion for single plane
body: <p><img src="https://i.stack.imgur.com/3dlhX.png" alt="enter image description here">
  This is the image I want to calibrate. The distance and angle is always fixed. With the normal method, I am able to calibrate the radial distortion to an extent(even using this one single image). But I am unable to remove the trapezoidal distortion. To avoid the problem of the corners not being detected properly, I am clicking all the corners manually using <code>setMouseCallback</code>. But still the problem persists.</p>