RGB to HSL

The R,G,B values are divided by 255 to change the range from 0..255 to
0..1:

R' = R/255

G' = G/255

B' = B/255

Cmax = max(R', G', B')

Cmin = min(R', G', B')

Δ = Cmax - Cmin

Hue calculation:

Saturation calculation:

Lightness calculation:

L = (Cmax + Cmin) / 2

HSL to RGB

When 0 ≤ H < 360, 0 ≤ S ≤ 1 and 0 ≤ L ≤ 1:

C = (1 - |2L - 1|) × S

X = C × (1 - |(H / 60º) mod 2 - 1|)

m = L - C/2

(R,G,B) = (R'+m, G'+m, B'+m)

算法参考来源：http://www.rapidtables.com/convert/color/index.htm

Code:

RGB TO HSL

function  [H,S,L]=RgbToHsl(Image_Input)



Image_Input=double(Image_Input)/255;

R_Input=Image_Input(:,:,1);

G_Input=Image_Input(:,:,2);

B_Input=Image_Input(:,:,3);

[heigth,width]=size(R_Input);

S(1:heigth,1:width)=0;

H(1:heigth,1:width)=0;

L(1:heigth,1:width)=0;



for i=1:heigth

    for j=1:width

        temp=[R_Input(i,j),G_Input(i,j),B_Input(i,j)];

        Max_value=max(temp);

        Min_value=min(temp);

        C_value=Max_value-Min_value;

        L(i,j)=(Max_value+Min_value)/2;

        if(C_value==0)

            S(i,j)=0;

        else 

            S(i,j)=C_value/(1-abs(2*L(i,j)-1));

        end  

        X=R_Input(i,j);

        Y=G_Input(i,j);

        Z=B_Input(i,j);

        if(C_value==0)

            continue;

        end

        if(Max_value==X)

            H(i,j)=mod((Y-Z)/C_value,6);

        elseif(Max_value==Y)

            H(i,j)=(Z-X)/C_value+2;

        else

            H(i,j)=(X-Y)/C_value+4;

        end

        H(i,j)=H(i,j)/6;

    end

end

HSL to RGB

function Image_out=HslToRgb(H,S,L)



%% H(0,1),S(0,1),L(0,1)

[height,width]=size(H);

R(1:height,1:width)=0;

G(1:height,1:width)=0;

B(1:height,1:width)=0;



for i=1:height

    for j=1:width

        C=(1-abs(2*L(i,j)-1))*S(i,j);

        X=C*(1-abs(mod(H(i,j)*6,2)-1));

        m=L(i,j)-C/2;

        temp=floor(H(i,j)*6+1);     

     switch(temp)

            case 1

                R(i,j)=C+m;

                G(i,j)=X+m;

                B(i,j)=m;

            case 2

                R(i,j)=X+m;

                G(i,j)=C+m;

                B(i,j)=m;

            case 3

                R(i,j)=m;

                G(i,j)=C+m;

                B(i,j)=X+m;

            case 4

                R(i,j)=m;

                G(i,j)=X+m;

                B(i,j)=C+m;

            case 5

                R(i,j)=X+m;

                G(i,j)=m;

                B(i,j)=C+m;

            case 6

                R(i,j)=C+m;

                G(i,j)=m;

                B(i,j)=X+m;

        end

    end

end

Image_out(:,:,1)=R;

Image_out(:,:,2)=G;

Image_out(:,:,3)=B;