色彩转换——RGB & HSL

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;