source code:

import cv2tracker = cv2.TrackerKCF_create()
video = cv2.VideoCapture(1)while True:ret,frame = video.read()cv2.imshow("source frame",frame)k = cv2.waitKey(30)if k == 'q':break bbox = cv2.selectROI(frame, False)
ok = tracker.init(frame,bbox)
cv2.destroyWindow("ROI Selector")while True:ret, frame = video.read()ret, bbox = tracker.update(frame)if ret:p1 = (int(bbox[0]),int(bbox[1]))p1 = (int(bbox[0]+bbox[2]),int(bbox[1]+bbox[3]))cv2.rectangle(frame, p1,p2,(0,0,255),2,2)cv2.imshow("Tracking", frame)k = cv2.waitkey(1)if k == 27:break