im=imread('0.bmp'); %讀圖
ir=imresize(im,1/2); 
f=figure; %截取紅色色塊
imshow(ir); 
t1=getrect(f); 
ic1=imcrop(ir,t1);
r1=ic1(:,:,1);%顯示紅色色塊的r、g、b分量
g1=ic1(:,:,2);
b1=ic1(:,:,3);
r=ir(:,:,1);%顯示原圖的r、g、b分量
g=ir(:,:,2);
b=ir(:,:,3);
[m n]=size(ir(:,:,1));%對原圖ir進行yuv轉換
A=[0.299 0.587 0.114;-0.148 -0.289 0.437;0.615 -0.515 0.100];
y=zeros(size(ir));
u=zeros(size(ir));
v=zeros(size(ir));
for i=1:m
   for j=1:n
x=A*[double(r(i,j));double(g(i,j));double(b(i,j))];
y(i,j)=x(1);
u(i,j)=x(2);
v(i,j)=x(3);
   end
end
[p,q]=size(r1(:,:,1));%對紅塊ic1進行yuv轉換
A=[0.299 0.587 0.114;-0.148 -0.289 0.437;0.615 -0.515 0.100];
y1=zeros(size(r1));
u1=zeros(size(r1));
v1=zeros(size(r1));
for a=1:p
   for b=1:q
k=A*[double(r1(a,b));double(g1(a,b));double(b1(a,b))];
y1(a,b)=k(1);
u1(a,b)=k(2);
v1(a,b)=k(3);
   end
end
y1max=max(max(y1));    %求出y的極大和極小值
y1min=min(min(y1));
u1max=max(max(u1));       %求出u的極大和極小值
u1min=min(min(u1)); 
v1max=max(max(v1));      %求出v的極大和極小值
v1min=min(min(v1));
yuv=zeros(m,n);
for i=1:m
    for j=1:n
      %if(((double(y1min)-0)<y(i,j))&(y(i,j)<(double(y1max)+0)))%未經校正
      %if(((double(u1min)-0)<u(i,j))&(u(i,j)<(double(u1max)+0)))
      %if(((double(v1min)-0)<v(i,j))&(v(i,j)<(double(v1max)+0)))  
      if(((double(y1min)-30)<y(i,j))&(y(i,j)<(double(y1max)+30)))%經過校正后
      if(((double(u1min)-2)<u(i,j))&(u(i,j)<(double(u1max)+2)))
      if(((double(v1min)-2)<v(i,j))&(v(i,j)<(double(v1max)+2)))   
                  yuv(i,j)=1;
      end
      end
      end
   end 
end
figure;
imshow(yuv) ;