Matlab

hsize= 31;
sigma =5;
h=fspecial('gaussian',hsize,sigma);
surf(h);
imagesc(h);
outim=imfiler(im,h);
imshow(outim);

for sigma= 1:3:10
h= fspecial('gaussian',fsize,sigma);
out = imfilter(im,h);
imshow(out);
pause;
end

Remove Noise

% Remove noise with a Gaussian Filter
%% load an image
img=imread('a.jpg');
imshow(img)'

%% add some noise
noise_sigma=25;
noise =randn(size(img)).*noise_sigma;
noisy_img=img+noise;
imshow(noisy_img);

%% create a gaussion filter
filter_size=11;
filter_sigma=2;
pkg_ load image;
filter = fspecial('gaussian', filter_size, filter_sigma);
%% apply it to remove noise
smoothed=imfilter(noisy_img,filter);