car detector in image

''''

for the xml file

.................................................................................................................................

https://raw.githubusercontent.com/andrewssobral/vehicle_detection_haarcascades/master/cars.xml

''''

import cv2

img_file = '3058.jpg'

classifier_file ='car_detector.xml'

img = cv2.imread(img_file)

bw = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

car_tracker = cv2.CascadeClassifier(classifier_file)

cars  = car_tracker.detectMultiScale(bw)

for (x,y,w,h) in cars:

    cv2.rectangle(img, (x,y),(x+w,y+h), (0,0,255),2)

cv2.imshow('car detector machine', img)

cv2.waitKey()

print ("code completed")

hears the screanshot.