test_webcam.py

import cv2, numpy

#Create object to read images from camera 0
cam = cv2.VideoCapture(0)

while True:
    #Get image from webcam
    ret, img = cam.read()
    
    #create some test points
    pts1 = numpy.array([[0,0],[100,100]], numpy.int32)
    pts2 = numpy.array([[0,0],[0,500],[200,200]], numpy.int32)
    pts3 = numpy.array([[10,3],[10,300],[100,250]], numpy.int32)
    
    #test out line function
    for i in xrange(len(pts3)-1):
        cv2.line(img,tuple(pts3[i]),tuple(pts3[i+1]), (255,255,255),1)
        
    #test out the polylines function
    cv2.polylines(img, [pts1, pts2], False, (255,255,255),1)
        
    #show the result
    cv2.imshow("Camera", img)

    #Sleep infinite loop for ~10ms
    #Exit if user presses <Esc>
    if cv2.waitKey(10) == 27:
        break