Get Image Pixel Values

Hello I am trying the values on image:

x=x+y;
y=x+2*y;

for all pixel values for an image,i want to get the pixel values do that i can verify the above equations.

code:

a=[1,1;1,2];
for i=1:m 
    for j=1:m 
        r=mod(a*[i;j],m); 
        ggg(i,j)=g(r(1),r(2));

PROBLEM:

g is original square image of size m in color but i get ggg in grayscale?

What problem exist? how to get the proper code

Thanks

Answer 1

[Walter Roberson]

ggg(i,j,:)=g(r(1),r(2),:);