title: How to use circle detect in a video
body: <p>I'm very new to python and OpenCV. What I am trying to do is find a circle on a part in a video using the hough circles and track that circle as it moves across the cameras field of view. I can use the hough circles on a still image. This is what I have so far, but I don't think it is anywhere close to being working. </p>
  
  <pre><code>import cv2
  import numpy as np
  
  img = cv2.VideoCapture(0)
  
  circles = cv2.HoughCircles(img,cv2.cv.CV_HOUGH_GRADIENT,1,20,
                          param1=200,param2=100,minRadius=0,maxRadius=0)
  
  circles = np.uint16(np.around(circles))
      for i in circles[0,:]:
      # draw the outer circle
      cv2.circle(cimg,(i[0],i[1]),i[2],(0,255,0),2)
      # draw the center of the circle
      cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3)
  
  cv2.imshow('detected circles',img)
  
  cv2.waitKey(0)
  cv2.destroyAllWindows()
  </code></pre>