import numpy as np
import matplotlib.pyplot as plt

img_orig   = plt.imread('Untitled 25.png')

# r, g, b, a = np.moveaxis(imgorig, 2, 0)
three      = np.moveaxis(img_orig, 2, 0)[:3]
three_flat = [x.flatten() for x in three]
names      = ('r', 'g', 'b')

if True:
    plt.figure()
    for i, (img, name) in enumerate(zip(three, names)):
        plt.subplot(2, 3, i+1+0)
        plt.imshow(img, vmin=0, vmax=1, cmap='gray')
        plt.title(name, fontsize=16)
    for i in range(3):
        plt.subplot(2, 3, i+1+3)
        plt.plot(three_flat[(i+0)%3], three_flat[(i+1)%3], '.k')
        plt.title(names[(i+1)%3] + ' vs ' + names[(i+0)%3], fontsize=16)
    plt.show()