如何在opencv python中为摄像头视频赋予透明边框？

import cv2
import numpy as np

def add_transparent_border(frame, border_size):
    # 获取视频帧的宽度和高度
    height, width, _ = frame.shape

    # 创建一个与视频帧大小相同的透明边框
    border = np.zeros((height, width, 4), dtype=np.uint8)

    # 将视频帧复制到透明边框中心
    border[border_size:height-border_size, border_size:width-border_size, :3] = frame

    # 将边框区域的Alpha通道设置为0，实现透明效果
    border[:, :, 3] = np.where((border[:, :, :3] != 0).any(2), 255, 0)

    return border

cap = cv2.VideoCapture(0)  # 打开摄像头，参数为摄像头索引号，0表示默认摄像头

while True:
    ret, frame = cap.read()  # 读取视频帧
    if not ret:
        break

    # 调用函数添加透明边框
    border_frame = add_transparent_border(frame, 20)

    # 显示带有透明边框的视频帧
    cv2.imshow('Video', border_frame)

    if cv2.waitKey(1) == ord('q'):  # 按下 'q' 键退出循环
        break

cap.release()  # 释放摄像头
cv2.destroyAllWindows()  # 关闭窗口