Laplacian sharpening filter in frequency domain

Hello everybody, I have written a code to do sharpening in frequency domain with Laplacian filter. The point is theLaplacian must be be between-1,1. Therefore it was divided to its max. I don’t know why it doesn’t work. I was wondering if anyone has any experience how to fix this problem? clear close all clc

a=imread('moon.tif'); a=im2double(a);

subplot(2,3,1); imshow(a); title('Input image');

[m,n]=size(a); A=fft2(a); subplot(2,3,2); imshow(uint8(abs(A))); title('F.T. of i/p without shift');

A_shift=fftshift(A); A_real=abs(A_shift); subplot(2,3,3); imshow(uint8(A_real)); title('F.T. of i/p after shift');

A_high=zeros(m,n); D=zeros(m,n);

for u=1:m for v=1:n H(u,v)=-4*(pi^2)*((u-(m./2))^2+(v-(n./2))^2);

    end
end

% Get maximum value of Laplacian max_val = max(abs(H),[],'all');

% Normalize Laplacian to range [-1,1] H_normalized = H / max_val;

% Compute inverse Fourier transform Laplacian_inverse = ifft2((H_normalized.*A_shift));

% Get real part of Laplacian inverse Laplacian_real = abs(Laplacian_inverse);

subplot(2,3,4); imshow(H); title('Laplacian filter');

subplot(2,3,5); mesh(H) title('Surface plot BHPF');

subplot(2,3,6); imshow(uint8(Laplacian_real)); title('Laplacian HP filtered image');