pkg load image

clear
clc

I = imread('Lena256color.jpg');

Ired = I(:,:,1);
Igreen = I(:,:,2);
Iblue = I(:,:,3);



subplot(2,3,1), imshow(I,[0 255]), title('Original')
subplot(2,3,4), imhist(Ired), title('Red histogram')
subplot(2,3,5), imhist(Igreen), title('Green histogram')
subplot(2,3,6), imhist(Iblue), title('Blue histogram')