title: Cropping live video feed in OpenCV
body: <p>I have a live video feed that tracks green objects and draws a rectangle over the object's area. I'm curious as to how I would be able to crop the feed to only show the area that the rectangle encompasses. </p>
  
  <p>Here's the section of relevance:</p>
  
  <pre><code>while True: 
  
      (success, frame) = webcam.read()
  
      frame = imutils.resize(frame, width = 1000)
      hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
  
      mask = cv2.inRange(hsv, greenLower, greenUpper)
      mask = cv2.erode(mask, None, iterations=2)
      mask = cv2.dilate(mask, None, iterations=2)
  
      cnts = cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)[-2]
      center = None
  
      if len(cnts) &gt; 0:
  
          c = max(cnts, key=cv2.contourArea)
          ((x, y), radius) = cv2.minEnclosingCircle(c)
          M = cv2.moments(c)
          center = (int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))
  
      for c in cnts:
          if cv2.contourArea(c) &lt; 500:
              continue
  
          (x, y, w, h) = cv2.boundingRect(c)
          cv2.rectangle(frame, (x,y), (x+w, y+h), (0, 255, 0), 2)
  
      pts = deque(maxlen = 32)
      pts.appendleft(center)
  
      for i in xrange(1, len(pts)):
  
          if pts[i - 1] is None or pts[i] is None:
              continue
  
          thickness = int(np.sqrt(args["buffer"] / float(i + 1)) * 2.5)
          cv2.line(frame, pts[i - 1], pts[i], (0, 255, 0), thickness)
  
      cv2.imshow("Presentation Tracker", frame)
  </code></pre>