#!/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)