title: Extract all bounding boxes using OpenCV Python
body: <p>I have an image that contains more than one bounding box.<br>
  <img src="https://i.imgur.com/4zuorgQ.jpg" alt="Books in Bounding Boxes"></p>
  
  <p>I need to extract everything that has bounding boxes in them.  So far, from this site I've gotten this answer:</p>
  
  <pre><code>y = img[by:by+bh, bx:bx+bw]
  cv2.imwrite(string + '.png', y)
  </code></pre>
  
  <p>It works, however, it only gets one.  How should I modify the code?  I tried putting it in the loop for contours but it still spews out one image instead of multiple ones.</p>
  
  <p>Thank you so much in advance.</p>