import numpy as np
import matplotlib.pyplot as plt
import matplotlib.image as mpimg



def rgb2gray(rgb):
    return np.dot(rgb[...,:3], [0.299, 0.587, 0.114])

img = mpimg.imread('Hamburger_sandwich.jpg')
gray = rgb2gray(img)
plt.imshow(gray, cmap = plt.get_cmap('gray'))


#imgplot = plt.imshow(img)
#lum_img = img[:,:,0]
#plt.imshow(lum_img)
#plt.imshow(lum_img, cmap="hot")
#imgplot = plt.imshow(lum_img)
#imgplot.set_cmap('nipy_spectral')
#imgplot = plt.imshow(lum_img)
#plt.colorbar()
#plt.hist(img.ravel(), bins=256, range=(0.0, 1.0), fc='k', ec='k')
#imgplot = plt.imshow(lum_img, clim=(0.0, 0.7))
plt.show()