更正代码，因为代码出现以下异常：cv2.error: OpenCV(3.4.8) C:\projects\opencv-python\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

好的，以下是更正后的代码：

import cv2
import numpy as np

# 读取原始图像
img = cv2.imread('image.jpg')

if img is None:  # 判断图像是否读取成功
    print('Failed to read image!')
else:
    # 转换为灰度图像
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    # 边缘检测
    edges = cv2.Canny(gray, 50, 150, apertureSize=3)

    # 获取直线
    lines = cv2.HoughLines(edges, 1, np.pi/180, 200)

    # 计算角度
    angles = []
    for line in lines:
        for rho, theta in line:
            a = np.cos(theta)
            b = np.sin(theta)
            x0 = a*rho
            y0 = b*rho
            x1 = int(x0 + 1000*(-b))
            y1 = int(y0 + 1000*(a))
            x2 = int(x0 - 1000*(-b))
            y2 = int(y0 - 1000*(a))
            angle = np.arctan2(y2-y1, x2-x1)
            angles.append(angle)

    # 计算平均角度
    avg_angle = np.mean(angles)

    # 旋转校正
    rows, cols = img.shape[:2]
    M = cv2.getRotationMatrix2D((cols/2, rows/2), avg_angle*180/np.pi, 1)
    corrected_img = cv2.warpAffine(img, M, (cols, rows))

    # 显示结果
    cv2.imshow('Original Image', img)
    cv2.imshow('Corrected Image', corrected_img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

这里加入了判断语句，如果无法读取图像，则会输出错误信息。