% Create an image that is the shape of a 2-dimensional Gaussian density.
% Do 'help fspecial' for information on the fspecial function.
g2=fspecial('gaussian', [25 25 ],3);
imagesc(g2);
k=g2;

% Create an image with a sparse set of pixels turned on.
sparseim=zeros(100);
for i=1:10000
  sparseim(round(rand*99+1),round(rand*99+1))=rand;
end
subplot(1,2,1);
imagesc(sparseim);

% Use conv2 to do two-dimensional convolution in matlab, using the
% Gaussian kernel we created above. 
smoothim=conv2(sparseim,k);
subplot(1,2,2);
imagesc(smoothim);