% Hough 變換
i=imread('d:\test.bmp');
i=rgb2gray(i);
i_long =size(i,1);
i_width=size(i,2);
i_edge=edge(i,'robert');
i_hough=zeros(300,300);
theta_step=3.14*2/299;
theta=0:theta_step:2*3.14;

x_max=1;
x_min=1;
y_max=1;
y_min=1;

for x=1:i_long
   for y=1:i_width
     if i_edge(x,y)==1
     x_max=max(x_max,x);
     x_min=min(x_min,x);
     y_max=max(y_max,y);
     y_min=min(y_min,y);
     end
   end
end

p_min=sqrt(x_min^2+y_min^2);
p_max=sqrt(x_max^2+y_max^2);
p_step=2*p_max/299;
p=-p_max:p_step:p_max;

for x=1:i_long
    for y=1:i_width
        if i_edge(x,y)==1     %對(duì)于邊緣點(diǎn)進(jìn)行累加
           rou=x.*cos(theta)+y.*sin(theta);
            w=fix(rou./p_step)+151;
            l=fix(1+theta./theta_step);
            n=300.*(l-1)+w;
            i_hough(n)=i_hough(n)+1;
        end
    end
end

m=max(max(i_hough));
i_hough=(i_hough./m);
imshow(i_hough)