1 clear all;
 2 close all;
 3 clc;
 4 
 5 img=imread('lena_color.jpg');
 6 %img=mat2gray(img);  %任意区间映射到[0,1];
 7 [m n dim]=size(img);
 8 imshow(img);
 9 %%图像的RGB
10 img=double(img);
11 R=img(:,:,1);
12 G=img(:,:,2);
13 B=img(:,:,3);
14 
15 %%RGB2YCbCr
16 Y=zeros(m,n);    %亮度
17 Cb=zeros(m,n);   %彩度
18 Cr=zeros(m,n);   %浓度
19 matrix=[0.299 0.587 0.114;
20         -0.1687 -0.3313 0.5;
21         0.5 -0.4187 -0.0813];
22 for i=1:m
23    for j=1:n 
24         tmp=matrix*[R(i,j) G(i,j) B(i,j)]';
25         Y(i,j)=tmp(1);
26         Cb(i,j)=tmp(2)+128;
27         Cr(i,j)=tmp(3)+128;
28    end
29 end
30 
31 %%YCbCr2RGB
32 matrix=inv(matrix);
33 for i=1:m
34    for j=1:n 
35         tmp=matrix*[Y(i,j) Cb(i,j)-128 Cr(i,j)-128]';
36         R(i,j)=tmp(1);
37         G(i,j)=tmp(2);
38         B(i,j)=tmp(3);
39    end
40 end
41 
42 %%如果正反变换都没错的话，那么图像是不变的
43 img(:,:,1)=R;
44 img(:,:,2)=G;
45 img(:,:,3)=B;
46 figure;
47 imshow(uint8(img))