Create a image that goes from white to black

Hi everyone.

I want to create an image that have white in the middle and while it goes to the sides it gets darker.

An image like this but with variable rows and colums.

I have try whit this:

theta = linspace(0, 2*pi, 256);
I = repmat((-cos(theta) + 1)/2, [256 1]);
h = imshow(I); 

But i don't know how to change its size.

[KSSV]

What do you meanby changing size? You can play around with his right?

n = 256 ;   % change this 
theta = linspace(0, 2*pi,n);

[Julen Vicente Pipaon]

Yep you're rigth.

I get it now.

%Change rows
n = 1500 ;   % change this 
theta = linspace(0, 2*pi,n);

%Change colums
n1=1000 ; %Change this
I = repmat((-cos(theta) + 1)/2, [n1 1]);

h = imshow(I);

Thanks for answering.