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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)
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