face_detection.py

import cv2

# https://github.com/opencv/opencv/tree/master/data/haarcascades
face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_alt2.xml')
smile_cascade = cv2.CascadeClassifier('haarcascade_smile.xml')
eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')

cap = cv2.VideoCapture(0)

while True:
    ret, img = cap.read()
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, scaleFactor=1.05, minNeighbors=5, minSize=(50, 50))
    smiles = smile_cascade.detectMultiScale(gray, scaleFactor=1.05, minNeighbors=5, minSize=(50, 50))

    for (x, y, w, h) in faces:
        cv2.rectangle(img, (x, y), (x + w, y + h), (190, 0, 0), 2)

        roi_gray = gray[y: y + h, x: x + w]
        roi_color = img[y: y + h, x: x + w]

        eyes = eye_cascade.detectMultiScale(roi_gray, scaleFactor=1.05, minNeighbors=15)
        for (ex, ey, ew, eh) in eyes:
            cv2.rectangle(roi_color, (ex, ey), (ex + ew, ey + eh), (0, 190, 0), 2)

        smiles = smile_cascade.detectMultiScale(roi_gray, 1.5, 15)
        for (sx, sy, sw, sh) in smiles:
            cv2.rectangle(roi_color, (sx, sy), (sx + sw, sy + sh), (0, 0, 190), 2)

    cv2.imshow('img', img)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()