根据this link的第14页,高通巴特沃斯滤波器的等式是,
而且,根据Page#17,输出应该类似于以下内容,
现在,我已经查看了这个answer in SO,并使用链接的pdf文档中给出的公式编写了以下Matlab代码。
输出看起来与上面给出的输出不同。
我的源代码中可能存在哪些问题?
源代码
的main.m
clear_all();
I = gray_imread('cameraman.png');
n = 1;
Dh = 10;
[J, Kernel] = butterworth_hp(I, Dh, n);
imshowpair(I, J, 'montage');
butterworth_hp.m
function [out, kernel] = butterworth_hp(I, Dh, n)
height = size(I, 1);
width = size(I, 2);
I_fft_shifted = fftshift(fft2(double(I)));
[u, v] = meshgrid(-floor(width/2):floor(width/2)-1,-floor(height/2):floor(height/2)-1);
kernel = butter_hp_kernel(u, v, Dh, n);
I_fft_shift_filtered = I_fft_shifted .* kernel;
out = real(ifft2(ifftshift(I_fft_shift_filtered)));
out = (out - min(out(:))) / (max(out(:)) - min(out(:)));
out = uint8(255*out);
function k = butter_hp_kernel(u, v, D0, n)
uv = u.^2+v.^2;
Duv = uv.^0.5;
frac = D0./Duv;
p = 2*n;
denom = frac.^p;
A = 0.414;
k = 1./(1+A*denom);
答案 0 :(得分:0)
我已经解决了这个问题。
解决此问题的关键是函数ifftshow()
。
源代码
<强>的main.m 强>
clear_all();
I = gray_imread('cameraman.png');
Dh = 10;
n = 1;
[J, K] = butterworth_hpf(I, Dh, n);
imshowpair(I, K, 'montage');
%draw_multiple_images({I, J, K});
<强> ifftshow.m 强>
function out = ifftshow(f)
f1 = abs(f);
fm = max(f1(:));
out = f1/fm;
end
<强> butter_hp_kernel.m 强>
function k = butter_hp_kernel(I, Dh, n)
Height = size(I,1);
Width = size(I,2);
[u, v] = meshgrid( ...
-floor(Width/2) :floor(Width-1)/2, ...
-floor(Height/2): floor(Height-1)/2 ...
);
k = butter_hp_f(u, v, Dh, n);
function f = butter_hp_f(u, v, Dh, n)
uv = u.^2+v.^2;
Duv = sqrt(uv);
frac = Dh./Duv;
%denom = frac.^(2*n);
A=0.414; denom = A.*(frac.^(2*n));
f = 1./(1.+denom);
<强> butterworth_hpf.m 强>
function [out1, out2] = butterworth_hpf(I, Dh, n)
Kernel = butter_hp_kernel(I, Dh, n);
I_ffted_shifted = fftshift(fft2(I));
I_ffted_shifted_filtered = I_ffted_shifted.*Kernel;
out1 = ifftshow(ifft2(I_ffted_shifted_filtered));
out2 = ifft2(ifftshift(I_ffted_shifted_filtered));
end