%找出每個圓的上水平切線位置
function fin_hl(bw,y1,y2,y) 
for i=y:768;    
   a=bw(i,y1:y2); 
   border=find(a==0);  
   [num1,num2]=size(border); 
   if num2>=1;
       break;
   end
end
border=border+y1-1    
i