Viola-Jones face detection from webcam

vj.py

#!/usr/bin/env python

import cv2
import sys
import video

if __name__ == '__main__':

   try : fn = sys.argv[1]
   except : fn = 0

   cv2.namedWindow('cam')

   cap = video.create_capture(fn)

   flag, img = cap.read()

   cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

   fourcc = cv2.cv.CV_FOURCC(*'XVID')
   out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640, 480))


   total = 0.0
   frames = 0.0

   while True:

       flag, img = cap.read()

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

       n = 0

       # image, reject level, level weights
       for (x, y, w, h) in cascade.detectMultiScale(gray):

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

           roi_color = img[y : y + h, x : x + w]
           n += 1


       cv2.putText(img, "%d" % n, (0, 470), cv2.FONT_HERSHEY_SIMPLEX, 1, (255, 255, 255), 2, 16)

       out.write(img)

       cv2.imshow('cam', img)

       total += n
       frames += 1

       ch = cv2.waitKey(5)
       if ch == 27:
           break


   cap.release()
   out.release()
   cv2.destroyAllWindows()
   
   print "frames : %d\nfaces : %d\naverage : %f" % (frames, total, (total / frames))