如何计算两个摄像头之间的距离(opencv-python)？

import cv2
import numpy as np

# 打开摄像头
cap1 = cv2.VideoCapture(0)
cap2 = cv2.VideoCapture(1)

# 设置摄像头参数
cap1.set(cv2.CAP_PROP_FRAME_WIDTH, 640)
cap1.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)
cap2.set(cv2.CAP_PROP_FRAME_WIDTH, 640)
cap2.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)

# 创建StereoBM对象
stereo = cv2.StereoBM_create(numDisparities=16, blockSize=15)

while True:
    # 读取图像
    ret1, frame1 = cap1.read()
    ret2, frame2 = cap2.read()

    if ret1 and ret2:
        # 转换为灰度图像
        gray1 = cv2.cvtColor(frame1, cv2.COLOR_BGR2GRAY)
        gray2 = cv2.cvtColor(frame2, cv2.COLOR_BGR2GRAY)

        # 计算视差图像
        disparity = stereo.compute(gray1, gray2)

        # 显示视差图像
        cv2.imshow('Disparity', disparity)

        # 按下ESC键退出
        if cv2.waitKey(1) == 27:
            break

# 释放摄像头
cap1.release()
cap2.release()

# 关闭窗口
cv2.destroyAllWindows()