pkg load image
clear
clc

I1 = imread('lena.bmp');
I2 = imread('baboon.bmp');
I3 = imread('peppers.bmp');

Ir = uint8(zeros(256,256,3));

Ir(:,:,1) = I1;
Ir(:,:,2) = I2;
Ir(:,:,3) = I3;

Ibw1 = 0.33*Ir(:,:,1) + 0.33*Ir(:,:,2) + 0.33*Ir(:,:,3);
Ibw2 = 0.30*Ir(:,:,1) + 0.59*Ir(:,:,2) + 0.11*Ir(:,:,3);

diagR = diag(Ir(:,:,1));
diagG = diag(Ir(:,:,2));
diagB = diag(Ir(:,:,3));
  

subplot(2,3,1), imshow(Ir,[0 255]), title('Color')
subplot(2,3,2), imshow(Ibw1,[0 255]), title('BW1')
subplot(2,3,3), imshow(Ibw2,[0 255]), title('BW2')

subplot(2,3,4), plot(diagR), axis([0 256 0 256]), grid on, title('diagR')
subplot(2,3,5), plot(diagG), axis([0 256 0 256]), grid on, title('diagG')
subplot(2,3,6), plot(diagB), axis([0 256 0 256]), grid on, title('diagB')