from skimage import data,io
import matplotlib.pyplot as plt

img=data.coffee()
plt.figure('image')
io.imshow(img)
plt.title('coffee')
plt.show()

plt.figure('hist')
arr=img.flatten()
plt.hist(arr, bins=256, density=1,edgecolor='None',facecolor='blue')
plt.title('histogram')
plt.show()

import cv2
from skimage import data,io
img=data.coffee()
colormap1 = img
plt.imshow(colormap1)
chans=cv2.split(colormap1)
colors=("b", "g", "r")
plt.figure()
plt.title("Color histogram")
plt.xlabel("Bins")
plt.ylabel("Number of pixels")
for (chan, c) in zip(chans, colors):
hist=cv2.calcHist([chan], [0], None, [256], [0,256])
plt.plot(hist, color=c)
plt.xlim([0,256])
plt.show()