OpenCV_Circles.py

import cv2
import numpy as np

cap = cv2.VideoCapture(0)
while(True):
    ret, frame = cap.read()
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    gray = cv2.medianBlur(gray, 5)

    # Extract regions/pixels  of interest
    rows = gray.shape[0]
    # Find circles:
    circles = cv2.HoughCircles(gray, cv2.HOUGH_GRADIENT, 1, rows / 8,
                               param1=100, param2=30,
                               minRadius=1, maxRadius=30)

    # Found circles ? Draw on top of them
    if circles is not None:
        circles = np.uint16(np.around(circles))
        for i in circles[0, :]:
            center = (i[0], i[1])
            # circle center
            cv2.circle(frame, center, 1, (0, 100, 100), 3)
            # circle outline
            radius = i[2]
            cv2.circle(frame, center, radius, (255, 0, 255), 3)

    # Display orignal frame:
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()