import cv2from matplotlib import pyplot as pltimport numpy as npimg = cv2imreadcjpggray = cv2cvtColorimgcv2COLOR_BGR2GRAYhist = cv2calcHistgray0None2560256pltsubplot221 pltimshowimg gray plttitleImage

import cv2 from matplotlib import pyplot as plt

img = cv2.imread('c.jpg') gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) hist = cv2.calcHist([gray],[0],None,[256],[0,256])

plt.subplot(223), plt.imshow(img, 'gray'), plt.title('Image2') plt.subplot(224), plt.plot(hist), plt.title('Histogram-by-opencv'), plt.xlim([0, 256]) plt.show()