function k = gaussianKernel(sigma)

%return the vector ([1 2 1] ./ 4) convolved with itself (2*sigma^2 - 1) times(
%to approximate a Gaussian

k_base = [1 2 1]/4; k=k_base;
for i=1:round(2*sigma^2 - 1)
    k = conv(k,k_base);
end