# 範例：webcam灰階
import cv2

cap = cv2.VideoCapture(0)
if not cap.isOpened():
    raise RuntimeError("Cannot open webcam")

while True:
    ok, frame = cap.read()
    if not ok:
        break
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.imshow("webcam gray", gray)
    if cv2.waitKey(1) & 0xFF == ord("q"):
        break

cap.release()
cv2.destroyAllWindows()