# draw histogram in python. import cv2 import numpy as np img = cv2 . imread ( 'image.jpg' ) h = np . zeros ( ( 300 , 256 , 3 ) ) bins = np . arange ( 256 ) . reshape ( 256 , 1 ) color = [ ( 255 , 0 , 0 ) , ( 0 , 255 , 0 ) , ( 0 , 0 , 255 ) ] for ch , col in enumerate ( color ) : hist_item = cv2 . calcHist ( [ img ] , [ ch ] , None , [ 256 ] , [ 0 , 255 ] ) cv2 . normalize ( hist_item , hist_item , 0 , 255 , cv2 . NORM_MINMAX ) hist = np . int32 ( np . around ( hist_item ) ) pts = np . column_stack ( ( bins , hist ) ) cv2 . polylines ( h , [ pts ] , False , col ) h = np . flipud ( h ) cv2 . imshow ( 'colorhist' , h ) cv2 . waitKey ( 0 )