[python] Draw Histogram

# 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)