title: Find and draw the largest contour in opencv on a specific color (Python)
body: <p>Im trying to get the largest contour of a red book.
  I've got a little problem with the code because its getting the contours of the smallest objects (blobs) instead of the largest one and I can't seem to figure out why this is happening</p>
  
  <p>The code I use:</p>
  
  <pre><code>camera = cv2.VideoCapture(0)
  kernel = np.ones((2,2),np.uint8)
  
  while True:
      #Loading Camera
      ret, frame = camera.read()
  
      blurred = cv2.pyrMeanShiftFiltering(frame, 3, 3)
      hsv = cv2.cvtColor(blurred, cv2.COLOR_BGR2HSV)
  
      lower_range = np.array([150, 10, 10])
      upper_range = np.array([180, 255, 255])
      mask = cv2.inRange(hsv, lower_range, upper_range)
  
      dilation = cv2.dilate(mask,kernel,iterations = 1)
  
      closing = cv2.morphologyEx(dilation, cv2.MORPH_GRADIENT, kernel)
      closing = cv2.morphologyEx(dilation, cv2.MORPH_CLOSE, kernel)
  
      #Getting the edge of morphology
      edge = cv2.Canny(closing, 175, 175)
      _, contours,hierarchy = cv2.findContours(edge, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
  
      # Find the index of the largest contour
      areas = [cv2.contourArea(c) for c in contours]
      max_index = np.argmax(areas)
      cnt=contours[max_index]
  
      x,y,w,h = cv2.boundingRect(cnt)
      cv2.rectangle(frame,(x,y),(x+w,y+h),(0,255,0),2)
  
  
      cv2.imshow('threshold', frame)
      cv2.imshow('edge', edge)
  
      if cv2.waitKey(1) == 27:
          break
  
  
  camera.release()
  cv2.destroyAllWindows()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/yuyGo.png" rel="noreferrer">As you can see on this picture</a></p>
  
  <p>Hopefully there is someone who can help</p>