def delBlueBackground(img):
    # 滤波
    img = cv2.medianBlur(img, 3)
    # 去除蓝底
    img_hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
    lower_blue = np.array([100, 60, 46])
    upper_blue = np.array([124, 255, 255])
    img_gray_binary = cv2.inRange(img_hsv, lower_blue, upper_blue)
    img_mask = np.copy(img)
    img_mask[img_gray_binary != 0] = [0, 0, 0]
    return img_mask