python+opencv实现动态物体追踪

import cv2 
import numpy as np 
camera=cv2.VideoCapture(0) 
firstframe=None 
while True: 
  ret,frame = camera.read() 
  if not ret: 
    break 
  gray=cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY) 
  gray=cv2.GaussianBlur(gray,(21,21),0) 
  if firstframe is None: 
    firstframe=gray 
    continue 
   
  frameDelta = cv2.absdiff(firstframe,gray) 
  thresh = cv2.threshold(frameDelta, 25, 255, cv2.THRESH_BINARY)[1] 
  thresh = cv2.dilate(thresh, None, iterations=2) 
  # cnts= cv2.findContours(thresh.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE) 
   
  x,y,w,h=cv2.boundingRect(thresh) 
  frame=cv2.rectangle(frame,(x,y),(x+w,y+h),(0,0,255),2) 
  cv2.imshow("frame", frame) 
  cv2.imshow("Thresh", thresh) 
  cv2.imshow("frame2", frameDelta) 
  key = cv2.waitKey(1)&0xFF 
   
  if key == ord("q"): 
    break 
 
camera.release() 
cv2.destroyAllWindows()