legend11_b.m

matlab - image processing - butterworth low pass filter

% legend11 - Butterworth lowpass filter
clear;clc;
x=double(imread('Fig4.11(a).jpg'));
r=input('Enter cutoff frequency = ');
s=2;
[m n]=size(x);
for i=1:m;
    for j=1:n;
        w(i,j)=((i-(m/2))^2+(j-(n/2))^2)^(1/2);
        w1(i,j)=1/(1+((w(i,j)/(r))^(2*s)));
        x1(i,j)=((x(i,j)*((-1)^(i+j))));
    end
end
F2=fft2(x1);
k=(F2).*(w1);
t=ifft2(k);
t2=real(t);
[p q]=size(t2);
for i=1:p;
   for j=1:q;
        g(i,j)=((t2(i,j)*((-1)^(i+j))));
    end
end
figure,imshow(x,[]);title('original');
figure,imshow(w1);title('n=2,D0=r filter');
figure,imshow(g,[]);title('n=2,D0=r filter');