rgb=imread('lena.png');
YCbCr=rgb2ycbcr(rgb);
subplot(221),imshow(rgb),title('image');
Y=YCbCr(:,:,1);
Cb=YCbCr(:,:,2);
Cr=YCbCr(:,:,3);
ycbcrmap(:,:,1)=Y;
ycbcrmap(:,:,2)=128;
ycbcrmap(:,:,3)=128;
subplot(222),imshow(Y),title('Y');
ycbcrmap(:,:,1)=128;
ycbcrmap(:,:,2)=Cb;
ycbcrmap(:,:,3)=128;
Cbcomponent=ycbcr2rgb(uint8(ycbcrmap));
subplot(223),imshow(Cbcomponent),title('Cb');
ycbcrmap(:,:,1)=128;
ycbcrmap(:,:,2)=128;
ycbcrmap(:,:,3)=Cr;
Crcomponent=ycbcr2rgb(uint8(ycbcrmap));
subplot(224),imshow(Crcomponent),title('Cr');