pkg load image

clear
clc

I = imread('lena.bmp');
Icolor = uint8(zeros(256,256,3));

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

Icolor(1:128,1:128,1) = I(1:128,1:128);
Icolor(1:128,129:256,2) = I(1:128,129:256);
Icolor(129:256,1:128,3) = I(129:256,1:128);

Icolor(129:256,129:256,1) = I(129:256,129:256);
Icolor(129:256,129:256,2) = I(129:256,129:256);
Icolor(129:256,129:256,3) = I(129:256,129:256);

IcolorNeg = 255-Icolor;

subplot(1,3,1), imshow(I,[0 255]), title('Original')
subplot(1,3,2), imshow(Icolor,[0 255]), title('Color shades')
subplot(1,3,3), imshow(IcolorNeg,[0 255]), title('Color shades negative')