I=imread('Car.jpg');
[y,x,z]=size(I);
myI=double(I);
%%%%%%%%%%% RGB to HSI  %%%%%%%%
tic   % 測定算法執行的時間，開始計時

%%%%%%%%%%% 統計分析 %%%%%%%%%%%%%%%
%%%%%%%% Y 方向 %%%%%%%%%%
Blue_y=zeros(y,1);
for i=1:y
    for j=1:x
            if((myI(i,j,1)<=30)&&((myI(i,j,2)<=62)&&(myI(i,j,2)>=51))&&((myI(i,j,3)<=142)&&(myI(i,j,3)>=119))) 
% 藍色RGB的灰度范圍
               Blue_y(i,1)= Blue_y(i,1)+1;     % 藍色象素點統計          
           end  
    end       
end
[temp MaxY]=max(Blue_y);        % Y方向車牌區域確定
PY1=MaxY;
while ((Blue_y(PY1,1)>=5)&&(PY1>1))
       PY1=PY1-1;
end    
PY2=MaxY;
while ((Blue_y(PY2,1)>=5)&&(PY2<y))
       PY2=PY2+1;
end
IY=I(PY1:PY2,:,:);

%%%%%%%% X 方向 %%%%%%%%%% 
Blue_x=zeros(1,x);             % 進一步確定X方向的車牌區域
for j=1:x
    for i=PY1:PY2
            if((myI(i,j,1)<=30)&&((myI(i,j,2)<=62)&&(myI(i,j,2)>=51))&&((myI(i,j,3)<=142)&&(myI(i,j,3)>=119)))
               Blue_x(1,j)= Blue_x(1,j)+1;               
           end  
    end       
end

PX1=1;
while ((Blue_x(1,PX1)<3)&&(PX1<x))
       PX1=PX1+1;
end    
PX2=x;
while ((Blue_x(1,PX2)<3)&&(PX2>PX1))
       PX2=PX2-1;
end
PX1=PX1-2; % 對車牌區域的修正
PX2=PX2+2;

Plate=I(PY1:PY2,PX1-2:PX2,:);
t=toc % 讀取計時
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
figure,imshow(I);
figure,plot(Blue_y);grid
figure,plot(Blue_x);grid
figure,imshow(IY);
figure,imshow(Plate);