clear;
moon = imread('Fig4.28(a).jpg');
u = double(moon);
[nx ny] = size(u)
nshades = 256;

coeff = 1;          % Sharpen the image.
for k = 1:1         
    for j = 2:ny-1
        for i = 2:nx-1
            newu(i,j) = 1.2*u(i,j) - coeff*(u(i-1,j) -2*u(i,j) + u(i+1,j))...
                               - coeff*(u(i,j-1) -2*u(i,j) + u(i,j+1));
        end                  
    end
    u = newu;
end
moonsharpenmat = uint8(u);
imwrite(moonsharpenmat, 'moonsharpen.jpg');