function []=blatt4a()

%A=[1 0 1 1;0 1 1 1; 0 1 1 1; 0 0 1 0];
A=im2double(imread('cam11.tif'));

figure
imshow(A)

sigma=0.02;

B=blur(A,sigma);
figure
imshow(B)

sigma=0.1;

B=blur(A,sigma);
figure
imshow(B)

sigma=0.15;

B=blur(A,sigma);
figure
imshow(B)

end


function B=blur(A,sigma)

[n,m] = size(A);
y1 = linspace(0,1,m+1);
y1 = (y1(1:m) + y1(2:m+1))/2;
y2 = linspace(0,1,n+1);
y2 = (y2(1:n)+y2(2:n+1))/2;
[Y1,Y2]=meshgrid(y1,y2);
dA=1/n*1/m;


for i=1:m
   for j=1:n
      B(i,j)=0;
      for k=1:m
          for l=1:n
           B(i,j)=B(i,j) + A(k,l)*dA*f([Y1(i,j)-Y1(k,l),Y2(i,j)-Y2(k,l)],sigma);
          end
      end
   end
end

end


function  y=f(z,sigma)

   y=1/(2*pi*sigma^2)*exp(- (norm(z)^2/(2*sigma^2)));

end