function r=hgtrans(bw,r_num,theta_num)
%Hough變換
%bw 為二值化后的圖像，r_num 為Hough 直線截距的個數，
%theta_num 為Hough空間角度的個數
[m,n]=size(bw);
r_max=sqrt((m-1)^2+(n/2)^2);r_min=-n/2+1;
dr=(r_max-r_min)/(r_num-1); dtheta=pi/(theta_num-1);
%dr截距分辨率，dtheta角度分辨率

theta=8*dtheta:dtheta:(r_num-1)*dtheta;
theta=[theta,0:dtheta:7*dtheta];
s=sin(theta); c=cos(theta);
[i,j]=find(bw);
x=j-n/2;y=m-i;  %x,y為二值圖像在圖像空間實際的坐標
h=(x*c+y*s-r_min)/dr;
h=round(h);

r=zeros(r_num,theta_num);
for i=0:r_num-1
   y=(h==i);
   r(i+1,:)=sum(y);
end