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 R=img(:,:,1);
11 G=img(:,:,2);
12 B=img(:,:,3);
13 
14 %%图像的RGB2HSV
15 H=zeros(m,n);   %色相角
16 S=zeros(m,n);   %饱和度
17 V=zeros(m,n);   %明度
18 for i=1:m
19    for j=1:n
20        r=R(i,j);
21        g=G(i,j);
22        b=B(i,j);
23        MAX=max([r,g,b]);
24        MIN=min([r,g,b]);
25 
26        if MAX==MIN
27             H(i,j)=0;
28        elseif MAX==r && g>=b
29             H(i,j)=60*(g-b)/(MAX-MIN);
30        elseif MAX==r && g<b
31             H(i,j)=60*(g-b)/(MAX-MIN)+360;
32        elseif MAX==g
33             H(i,j)=60*(b-r)/(MAX-MIN)+120;
34        elseif MAX==b
35             H(i,j)=60*(r-g)/(MAX-MIN)+240;
36        end
37 
38        if MAX==0
39             S(i,j)=0;
40        else
41             S(i,j)=1-MIN/MAX;
42        end
43 
44        V(i,j)=MAX;
45    end
46 end
47 
48 %%图像HSV2RGB
49 for i=1:m
50     for j=1:n
51         h=floor(H(i,j)/60);
52         f=H(i,j)/60-h;
53         v=V(i,j);
54         s=S(i,j);
55         p=v*(1-s);
56         q=v*(1-f*s);
57         t=v*(1-(1-f)*s);
58 
59         if h==0
60             R(i,j)=v;G(i,j)=t;B(i,j)=p;
61         elseif h==1
62             R(i,j)=q;G(i,j)=v;B(i,j)=p;            
63         elseif h==2
64             R(i,j)=p;G(i,j)=v;B(i,j)=t;            
65         elseif h==3
66             R(i,j)=p;G(i,j)=q;B(i,j)=v;            
67         elseif h==4
68             R(i,j)=t;G(i,j)=p;B(i,j)=v;            
69         elseif h==5
70             R(i,j)=v;G(i,j)=p;B(i,j)=q;            
71         end
72     end
73 end
74 
75 %%如果正反变换都没错的话，那么图像是不变的
76 img(:,:,1)=R;
77 img(:,:,2)=G;
78 img(:,:,3)=B;
79 figure;
80 imshow(img)