1、理想低通濾波

參考代碼如下：

clear?all;close?all;

I=imread('eight.jpg');

I=im2double(I);

M=2*size(I,1);

N=2*size(I,2);

u=-M/2:(M/2-1);

v=-N/2:(N/2-1);

[U,V]=meshgrid(u,v);

D=sqrt(U.^2+V.^2);

D0=80;

H=double(D<=D0);

J=fftshift(fft2(I,size(H,1),size(H,2)));

K=J.*H;

L=ifft2(ifftshift(K));

L=L(1:size(I,1),1:size(I,2));

figure;

subplot(121);

imshow(I);

subplot(122);

imshow(L);

2、巴特沃斯低通濾波

參考代碼如下：

clear?all;close?all;

I=imread('tire.tif');

I=im2double(I);

M=2*size(I,1);

N=2*size(I,2);

u=-M/2:(M/2-1);

v=-N/2:(N/2-1);

[U,V]=meshgrid(u,v);

D=sqrt(U.^2+V.^2);

D0=50;

n=6;

H=1./(1+(D0./D).^(2*n));

J=fftshift(fft2(I,size(H,1),size(H,2)));

K=J.*H;

L=ifft2(ifftshift(K));

L=L(1:size(I,1),1:size(I,2));

figure;

subplot(121);

imshow(I);

subplot(122);

imshow(L);

3、巴特沃斯高通濾波

參考代碼如下：

clear?all;close?all;

I=imread('rice.png');

I=im2double(I);

M=2*size(I,1);

N=2*size(I,2);

u=-M/2:(M/2-1);

v=-N/2:(N/2-1);

[U,V]=meshgrid(u,v);

D=sqrt(U.^2+V.^2);

D0=30;

n=6;

H=1./(1+(D0./D).^(2*n));

J=fftshift(fft2(I,size(H,1),size(H,2)));

K=J.*H;

L=ifft2(ifftshift(K));

L=L(1:size(I,1),1:size(I,2));

figure;

subplot(121);

imshow(I);

subplot(122);

imshow(L);

同態(tài)濾波

參考代碼如下：

clear?all;close?all;

I=imread('pout.tif');

J=log(im2double(I)+1);

K=fft2(J);

n=5;

D0=0.1*pi;

rh=0.7;

r1=0.4;

[row,column]=size(J);

for?i=1:row

????for?j=1:column

????????D1(i,j)=sqrt(i.^2+j.^2);

????????H(i,j)=r1+(rh/(1+(D0/D1(i,j))^(2*n)));

????end

end

L=K.*H;

M=ifft2(L);

N=exp(M)-1;

figure;

subplot(121);

imshow(I);

subplot(122);

imshow(real(N));