从opencv Mat中读视频数据，用imshow显示了三个，应该怎么搞

从opencv Mat中读视频数据，用imshow显示了三个图像，怎么才能变成一个

https://blog.csdn.net/huanglu_thu13/article/details/52337014

# created by Huang Lu
# 27/08/2016 17:24:55
# Department of EE, Tsinghua Univ.

import cv2
import numpy as np

cap = cv2.VideoCapture("../test.avi")
while(1):
    # get a frame
    ret, frame = cap.read()
    # show a frame
    cv2.imshow("capture", frame)
    if cv2.waitKey(100) & 0xFF == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()