function imageblurred = Blur(image,levelblurring)
% returns a blurred version of image of blurring level levelblurring
%   image is the string (file name of the image to be blurred)
%   imageblurred is the matrix representing the blurred image
A = imread(image);
A = double(rgb2gray(A));
[m,n] = size(A);
% blurring: it uses a matrix B for the vertical blurring 
% and a matrix C for the horizontal blurring;
v = [1/4 1/2 1/4];
B = spdiags( repmat(v,m,1), [-1 0 1],m,m);
C = spdiags( repmat(v,n,1), [-1 0 1],n,n);
imageblurred = B^levelblurring * A * C^levelblurring;
end