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#!/usr/bin/env python

"""

Sample code for displaying image histogram with Matplotlib

"""

import cv2

import matplotlib.pyplot as plt

def show_histogram(im):

""" Function to display image histogram.

Supports single and three channel images. """

if im.ndim == 2:

# Input image is single channel

plt.hist(im.flatten(), 256, range=(0,250), fc='k')

plt.show()

elif im.ndim == 3:

# Input image is three channels

fig = plt.figure()

fig.add_subplot(311)

plt.hist(im[...,0].flatten(), 256, range=(0,250), fc='b')

fig.add_subplot(312)

plt.hist(im[...,1].flatten(), 256, range=(0,250), fc='g')

fig.add_subplot(313)

plt.hist(im[...,2].flatten(), 256, range=(0,250), fc='r')

plt.show()

if __name__ == '__main__':

im = cv2.imread("lena.jpg");

if not (im == None):

show_histogram(im)