text: #!/usr/bin/env python
  
  import cv2   as cv
  import numpy as np
  from umucv.stream import autoStream
  
  from collections import deque
  
  d = deque(maxlen=20)
  
  def bgr2gray(x):
      return cv.cvtColor(x,cv.COLOR_BGR2GRAY).astype(float)/255
  
  for key,frame in autoStream():
      d.append(bgr2gray(frame))
      cv.imshow('input',d[0])
      cv.imshow('delay',d[-1])
      cv.imshow('ghost',np.mean(d,axis=0))
  
  cv.destroyAllWindows()
  
  