数字图像-频域处理

冈萨雷斯第三版，频域处理代码示例：

% 低通滤波

clc, clear, 

I = imread('blown_ic.tif');

[r,c] = size(I);

subplot(331),imshow(I);title('Origin');

Id = padarray(I,[r,c],'post');

subplot(332),imshow(Id);title('pad array');

for i = 1:2*r

    for j = 1:2*c

        hp(i,j) = (-1)^(i-1+j-1);

    end

end

Ip = hp.*double(Id);

subplot(333),imshow(Ip,[]);title('shift array');

F = fft2(Ip);% padding of  H

subplot(334),imshow(log(1+abs(F)),[]);title('spectrum of F');

H = lpfilter('gaussian',2*r,2*c,50,1);% 

subplot(335),imshow(H,[]);title('H');

G = H.*F;

subplot(336),imshow(G);title('G=H.*F ');

gp = hp.*real(ifft2(G));% filtering

subplot(337),imshow(gp,[]);title('gp ');

g = gp(1:r,1:c);% cropped images

subplot(338),imshow(g,[]);title('g ');