python小白opencv程序运行报错

import cv2
import numpy as np
from matplotlib import pyplot as plt
img_bgr = 'D:\\OpencvWork\jqr.png'
img_lab = cv2.cvtColor(img_bgr, cv2.COLOR_BGR2LAB)
img_ls = img_lab[..., 0]
img_as = img_lab[..., 1]
img_bs = img_lab[..., 2]

# 分通道显示图片
fig = plt.gcf()
fig.set_size_inches(10, 15)

plt.subplot(221)
plt.imshow(img_lab)
plt.axis('off')
plt.title('L*a*b*')

plt.subplot(222)
plt.imshow(img_ls, cmap='gray')
plt.axis('off')
plt.title('L*')

plt.subplot(223)
plt.imshow(img_as, cmap='gray')
plt.axis('off')
plt.title('a*')

plt.subplot(224)
plt.imshow(img_bs, cmap='gray')
plt.axis('off')
plt.title('b*')

plt.show()

  报错信息：File "D:\PycharmProjects\pythonProject\demo5.py", line 8, in <module>
    img_lab = cv2.cvtColor(img_bgr, cv2.COLOR_BGR2LAB)
TypeError: Expected Ptr<cv::UMat> for argument 'src'

求大佬解答怎么改正

大兄弟，你的图片是个地址啊，要读取图片才行

img_bgr =cv2.imread( 'D:\\OpencvWork\jqr.png')