# load and display an image
import matplotlib.pyplot as plt

img = plt.imread("mandrill.jpg")
size = img.shape
plt.figure(figsize=(size[0]/72,size[1]/72)) # figure size is specified in inches, specify as pixels/pixels_per_inch
plt.imshow(img) # display the image
#plt.axis('off')
print( size )


# each pixel of an RGB image consists of three
R = img[:,:,0]
G = img[:,:,1]
B = img[:,:,2]

plt.subplot(131); plt.imshow(R); plt.axis('off');
plt.subplot(132); plt.imshow(G); plt.axis('off');
plt.subplot(133); plt.imshow(B); plt.axis('off');


# specify the colormap (mapping from value to color) when displaying grayscale images
R = img[:,:,0]
G = img[:,:,1]
B = img[:,:,2]

plt.subplot(131); plt.imshow(R, cmap='gray'); plt.axis('off'); plt.title( 'red' )
plt.subplot(132); plt.imshow(G, cmap='gray'); plt.axis('off'); plt.title( 'green' )
plt.subplot(133); plt.imshow(B, cmap='gray'); plt.axis('off'); plt.title( 'blue' )


# convert from RGB to gray and explore colormaps
gray = 0.2989*R + 0.5870*G + 0.1140*B
size = gray.shape
print(size)
plt.figure(figsize=(size[0]/72,size[1]/72)) # figure size is specified in inches, specify as pixels/pixels_per_inch
plt.imshow(gray,cmap='jet') # display the image
#plt.imshow(gray,cmap='rainbow')
#plt.imshow(gray,cmap='ocean')
#plt.imshow(gray,cmap='inferno')

plt.axis('off')
plt.colorbar()


# colormap limits
plt.subplot(121); 
plt.imshow(gray, cmap='jet')
plt.colorbar(ticks=[1, 100, 200], orientation='horizontal')
plt.axis('off'); 

plt.subplot(122);
h = plt.imshow(gray, cmap='jet')
h.set_clim(50, 150)
plt.colorbar(ticks=[50, 100, 150], orientation='horizontal')
plt.axis('off'); 


# histogram of intensity values (ravel converts 2-D to 1-D)
plt.hist(gray.ravel(), bins=256, range=(0.0, 255) );

R = img[:,:,0]
G = img[:,:,1]
B = img[:,:,2]

plt.figure(figsize=(10,5)) 
plt.subplot(131); plt.hist(R.ravel(), bins=256, range=(0.0, 255) ); plt.title( 'red' );
plt.subplot(132); plt.hist(G.ravel(), bins=256, range=(0.0, 255) ); plt.title( 'green' );
plt.subplot(133); plt.hist(B.ravel(), bins=256, range=(0.0, 255) ); plt.title( 'blue' );