reconstruction Error of 2 colored images

I have an original image of dimension 300x300x3 (RGB)

after removing some entries, I apply an algorithm to reconstuct the original image.

Now i want to find the relative error between the 2 images.

....
 % I call my function norm_fro to calcuate the error
Erec(i)= norm_fro( X_origin , X_r ecovered);
....
    
%  here is my norm_fro function
function f = norm_fro( X , Xhat )

f = norm(X -Xhat,'fro')^2/norm(X,'fro')^2;

end

I get this error

Error using norm
Input must be 2-D.

Error in norm_fro (line 11)
f = norm(X -Xhat,'fro')^2/norm(X,'fro')^2;