clear;
micro = imread('Fig4.04(a).jpg');
micro = double(micro);
[nx ny] = size(micro);
nx
ny
u = micro;
micro = uint8(u);
imwrite(micro, 'micro.jpg');
fftu = fft2(u,2*nx-1,2*ny-1);
fftu = fftshift(fftu);
subplot(1,2,1)
mesh(log(1+(abs(fftu))));
% Use Butterworth or Gaussian high pass filter.
filter = ones(2*nx-1,2*ny-1);
d0 = 100;      
n = 4;
for i = 1:2*nx-1
    for j =1:2*ny-1
        dist = ((i-(nx+1))^2 + (j-(ny+1))^2)^.5;
        % Use Butterworth high pass filter.
        filter(i,j)= 1/(1 + (dist/d0)^(2*n));
        filter(i,j)= 1.0 - filter(i,j);
        % Use Gaussian high pass filter.
        %filter(i,j) = exp(-dist^2/(2*d0^2));
        %filter(i,j) = 1.0 - filter(i,j);
    end
end
% Update image with high frequencies.
fil_micro  = fftu + filter.*fftu;
subplot(1,2,2)
mesh(log(1+abs(fil_micro-fftu)));
fil_micro = ifftshift(fil_micro);
fil_micro = ifft2(fil_micro,2*nx-1,2*ny-1);
fil_micro = real(fil_micro(1:nx,1:ny));
fil_micro = uint8(fil_micro);
imwrite(fil_micro, 'micro_fil.jpg');