MATLAB: Showing multiple images in one window in Matlab

Question

Why doesn't the following code show the images?

clear all;       
image_name = 'woman.png';
I = gray_imread(image_name);
N = 12;
J = zeros(size(I,1), size(I,2), N);
for i=1:N    
    J(:,:,i) = I;
end
sqrtt = ceil(sqrt(N));
m = sqrtt;
n = sqrtt;
for k=1:N
    K = J(:,:,k);
    subplot(m,n,k);
    imshow(K);
    set(gca,'xtick',[],'ytick',[])
end

How can I solve the issue?

Answer 1

Change

J = zeros(size(I,1), size(I,2), N);

to

J = zeros(size(I,1), size(I,2), N, class(I));