Python OpenCV 识别视频帧中第二大的黑色矩形

gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)  # 将帧转换为灰度图像
_, threshold = cv2.threshold(gray, 127, 255, cv2.THRESH_BINARY_INV)  # 对灰度图像进行二值化处理，反转黑白

contours, _ = cv2.findContours(threshold, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)  # 寻找轮廓
contours = sorted(contours, key=cv2.contourArea, reverse=True)  # 按轮廓面积排序

if len(contours) > 1:
    second_largest_contour = contours[1]  # 获取第二大的轮廓
    x, y, w, h = cv2.boundingRect(second_largest_contour)  # 获取轮廓的外接矩形

    x1, y1 = x, y
    x2, y2 = x + w, y
    x3, y3 = x + w, y + h
    x4, y4 = x, y + h

    x_center = (x1 + x2) / 2
    y_center = (y1 + y3) / 2

    cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)  # 在原始图像上绘制第二大矩形

    cv2.imshow('Second Largest Rectangle', frame)  # 显示带有矩形的图像
    print(f'x1: {x1}, y1: {y1}')
    print(f'x2: {x2}, y2: {y2}')
    print(f'x3: {x3}, y3: {y3}')
    print(f'x4: {x4}, y4: {y4}')