text: from __future__ import print_function
  import cv2 as cv
  import argparse
  
  parser = argparse.ArgumentParser(description='This program shows how to use background subtraction methods provided by \
                                                OpenCV. You can process both videos and images.')
  parser.add_argument('--input', type=str, help='Path to a video or a sequence of image.', default='vtest.avi')
  parser.add_argument('--algo', type=str, help='Background subtraction method (KNN, MOG2).', default='MOG2')
  args = parser.parse_args()
  
  ## [create]
  #create Background Subtractor objects
  if args.algo == 'MOG2':
      backSub = cv.createBackgroundSubtractorMOG2()
  else:
      backSub = cv.createBackgroundSubtractorKNN()
  ## [create]
  
  ## [capture]
  capture = cv.VideoCapture(cv.samples.findFileOrKeep(args.input))
  if not capture.isOpened():
      print('Unable to open: ' + args.input)
      exit(0)
  ## [capture]
  
  while True:
      ret, frame = capture.read()
      if frame is None:
          break
  
      ## [apply]
      #update the background model
      fgMask = backSub.apply(frame)
      ## [apply]
  
      ## [display_frame_number]
      #get the frame number and write it on the current frame
      cv.rectangle(frame, (10, 2), (100,20), (255,255,255), -1)
      cv.putText(frame, str(capture.get(cv.CAP_PROP_POS_FRAMES)), (15, 15),
                 cv.FONT_HERSHEY_SIMPLEX, 0.5 , (0,0,0))
      ## [display_frame_number]
  
      ## [show]
      #show the current frame and the fg masks
      cv.imshow('Frame', frame)
      cv.imshow('FG Mask', fgMask)
      ## [show]
  
      keyboard = cv.waitKey(30)
      if keyboard == 'q' or keyboard == 27:
          break
  