matlab練習程序（RGB2HSL、HSL2RGB）

　　色相飽和度亮度和三原色的相互轉換

function mainimg=imread('lena_color.jpg');img=mat2gray(img);  %任意區間映射到[0,1];[m n dim]=size(img);imshow(img);%%圖像的RGBR=img(:,:,1);G=img(:,:,2);B=img(:,:,3);%%圖像RGB2HSLH=zeros(m,n);   %色相角S=zeros(m,n);   %飽和度L=zeros(m,n);   %亮度for i=1:mfor j=1:nr=R(i,j);g=G(i,j);b=B(i,j);MAX=max([r,g,b]);MIN=min([r,g,b]);if MAX==MINH(i,j)=0;elseif MAX==r && g>=bH(i,j)=60*(g-b)/(MAX-MIN);elseif MAX==r && g<bH(i,j)=60*(g-b)/(MAX-MIN)+360;elseif MAX==gH(i,j)=60*(b-r)/(MAX-MIN)+120;elseif MAX==bH(i,j)=60*(r-g)/(MAX-MIN)+240;endL(i,j)=(MAX+MIN)/2;if L(i,j)==0 || MAX==MINS(i,j)=0;elseif 0<L(i,j) && L(i,j)<=0.5S(i,j)=(MAX-MIN)/(2*L(i,j));elseif L(i,j)>0.5S(i,j)=(MAX-MIN)/(2-2*L(i,j));endendendwa=waitbar(0,'wait');%%圖像HSL2RGBfor i=1:mfor j=1:ns=S(i,j);   l=L(i,j);         if s~=0h=H(i,j);      if l<0.5q=l*(1+s);elseq=l+s-(l*s);endp=2*l-q;hk=h/360;tR=hk+1/3;tG=hk;tB=hk-1/3;R(i,j)=foo(tR,p,q);G(i,j)=foo(tG,p,q);B(i,j)=foo(tB,p,q);elseR(i,j)=l;G(i,j)=l;B(i,j)=l;endendwaitbar(i/m);endclose(wa);function re=foo(t,p,q)if t<0t=t+1.0;elseif t>1t=t-1.0;endif t<1/6re=p+((q-p)*6*t);elseif 1/6<=t && t<0.5re=q;elseif 0.5<=t && t<2/3re=p+((q-p)*6*(2/3-t));elsere=p;endend    %%如果正反變換都沒錯的話，那么圖像是不變的img(:,:,1)=R;img(:,:,2)=G;img(:,:,3)=B;figure;imshow(img)end

參考：http://zh.wikipedia.org/wiki/HSV_%E8%89%B2%E5%BD%A9%E7%A9%BA%E9%97%B4#.E4.BB.8E_HSV_.E5.88.B0_RGB_.E7.9A.84.E8.BD.AC.E6.8D.A2