%--------------------------------------------------------
%函數說明：
%輸入：
%           image: 讀入圖片的路徑
%           D0:      參數D0
%           n:        巴特沃思與指數濾波器的階數
%輸出：
%           經過各種濾波后的圖片
%--------------------------------------------------------

function HPFilter (image , D0 , n);

%image = 'lena_noise.bmp';
f = imread(image);
[u,v] = size(f);
mid_x = u/2;
mid_y = v/2;
%D0 = 50;

%----------------------------------------------------------
%高通濾波器的設計
%----------------------------------------------------------
figure;
subplot(2,2,1);
imshow(f);
title('原圖');
%-------------------------------
%理想高通濾波器（ILPF）
%-------------------------------
H = zeros(u,v);
for i = 1:u
    for j = 1:v
        if(sqrt((i-mid_x)^2+(j-mid_y)^2) > D0)
            H(i,j) = 1;
        end
    end
end

g = myfilter (f, H, D0);
subplot(2,2,2);
imshow(g);
title('理想高通濾波');

%-------------------------------
%巴特沃思高通濾波器（BLPF）
%-------------------------------
for i = 1:u
    for j = 1:v
        H(i,j) = (1+(D0^2/(i^2+j^2))^n)^-1;
    end
end

g = myfilter (f, H, D0);
subplot(2,2,3);
imshow(g);
title('巴特沃思高通濾波');

%-------------------------------
%指數高通濾波器（elpf）
%-------------------------------
for i = 1:u
    for j = 1:v
        H(i,j) = exp(-(D0^2/(i^2+j^2))^n);
    end
end

g = myfilter (f, H, D0);
subplot(2,2,4);
imshow(g);
title('指數高通濾波');