OpenCV-Python draw histograms and cumulative histograms

code show as below:

import cv2
import numpy as np
import matplotlib.pyplot as plt

img = cv2.imread('C:\\Users\\admin\\Desktop\\original_img3\\testimg\\messi.jpg')
_, _, colorChannel = img.shape
color = ['B', 'G', 'R']
plt.figure()
for i in range(colorChannel):
    hist_img, _ = np.histogram(img[:, :, i], 256)
    plt.plot(range(256), hist_img, label=color[i])
    plt.legend (loc = 'best')
    plt.title('histogram')

plt.figure()
for i in range(colorChannel):
    hist_img, _ = np.histogram(img[:, :, i], 256)
    cdf_img = np.cumsum(hist_img)   # accumulative histogram
    plt.plot(range(256), cdf_img, label=color[i])
    plt.legend (loc = 'best')
    plt.title('accumulative histogram')

Results are as follows: