【数字图像处理matlab】RGB转HIS，HIS转RGB

读入一张RGB图像，将其转换为HIS，再将HIS转换为RGB。

function F=color_processing(image)
%调用代码-----------------------------------------
%imageR=imread('flower.jpg');  
%image=im2double(imageR);color_processing(image);
%------------------------------------------------

%RGB->HIS变换,rgb2hsv()
%从三维数组中提取三幅分量图像
R1=image(:,:,1);
G1=image(:,:,2);
B1=image(:,:,3);
I=(R1+G1+B1)/3;        %亮度分量，范围[0,1]
m=min(min(R1,G1),B1);
S=1-3*m./(R1+G1+B1);    %饱和度分量，范围[0,1]
theta=acos(((R1-G1)+(R1-B1))./(2*((R1-G1).^2+((R1-B1).*(G1-B1))).^(1/2))); %弧度 
H=theta;   %色度分量，以角度表示，范围是[0,1]（弧度除以2*pi后）
if B1>G1
    H=2*pi-theta;       
end     
if S==0
    H=0;
end
H=H/(2*pi);
Image1=cat(3,H,S,I);
subplot(1,3,1),imshow(image);
title('RGB原图')
subplot(1,3,2),imshow(Image1);
title('转换后的HSI图像')

%HIS->RGB变换,Image1转为imdouble型

H1=Image1(:,:,1)*2*pi;  %弧度
S1=Image1(:,:,2);
I1=Image1(:,:,3);

R1 = zeros(size(Image1, 1), size(Image1, 2)); 
G1= zeros(size(Image1, 1), size(Image1, 2)); 
B1 = zeros(size(Image1, 1), size(Image1, 2));

i= find( (0 <= H1) & (H1 < 2*pi/3)); 
B1(i) = I1(i) .* (1 - S1(i)); 
R1(i) = I1(i) .* (1 + S1(i) .* cos(H1(i)) ./ cos(pi/3 - H1(i))); 
G1(i) = 3*I1(i) - (R1(i) + B1(i)); 

i = find( (2*pi/3 <= H1) & (H1 < 4*pi/3) ); 
R1(i) = I1(i) .* (1 - S1(i)); 
G1(i) = I1(i) .* (1 + S1(i) .* cos(H1(i) - 2*pi/3) ./ cos(pi - H1(i))); 
B1(i) = 3*I1(i) - (R1(i) + G1(i)); 

i = find( (4*pi/3 <= H1) & (H1 <= 2*pi)); 
G1(i) = I1(i) .* (1 - S1(i)); 
B1(i) = I1(i) .* (1 + S1(i) .* cos(H1(i) - 4*pi/3) ./cos(5*pi/3 - H1(i))); 
R1(i) = 3*I1(i) - (G1(i) + B1(i)); 

Image2 = cat(3, R1, G1, B1); 
Image2 = max(min(Image2, 1), 0); 
subplot(1,3,3),imshow(Image2);
title('转换回的RGB图像') 


end

测试：