title: efficiency way to get the coordinate of each rectangle box
body: <p>I am trying to get the coordinates from a Zoom image.
  Suppose there are 20 &quot;boxes&quot; inside Zoom image.  Is there any way to
  get each box coordinate (upper left, upper right, lower left, lower right)?</p>
  <p>I am trying different methods likes Canny edge detection / erosion by Python opencv
  but it will also get the &quot;content&quot; inside the zoom image box which I don't expect to use.
  I only need the &quot;red circle&quot; (ref to the image)</p>
  <p><a href="https://i.stack.imgur.com/NgcjZ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NgcjZ.png" alt="enter image description here" /></a>
  <a href="https://i.stack.imgur.com/u2iMn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/u2iMn.png" alt="enter image description here" /></a></p>
  <p>Thanks
  Alex</p>