Mutual conversion of RGB and HSL colors

Transferred from: http://blog.csdn.net/aniven/article/details/2205851

RGB and HSL (also called HSB/HSV) are two color spaces, namely: red, green, Blue (red,green,blue) and hue, saturation, brightness (Hue,saturation,lightness or brightness or value), the former is suitable for machine sampling, the current display color is composed of these three colors, and the latter more in line with human visual sense, such as people generally express a color will say: a little thick dark red. Not to say how much red, green accounted for how much, blue accounted for.
Both of these representations are included in the standard Color dialog box for Windows. The RGB value range is between 0~255, HSL's value is between 0~1, but the Windows system is processed into a range of 0~240 values, the values in various environments refer to the schedule. In addition there are cmy/cmyk color space, often used in the printing industry, and then the Rgb-cmy-cmyk conversion algorithm posted.

Convert RGB to HSL:
#include <algorithm>
Using Std::min;
Using Std::max;

void RGB2HSL (TColor acolor, double &h,double &s,double &l)
{
Double R,g,b,max,min,del_r,del_g,del_b,del_max;
R = Getrvalue (acolor)/255.0; Where RGB values = 0÷255
G = Getgvalue (acolor)/255.0;
B = Getbvalue (acolor)/255.0;

min = min (R, min (G, B)); Min. Value of RGB
max = max (R, Max (G, B)); Max. Value of RGB
Del_max = Max-min; Delta RGB Value

L = (Max + Min)/2.0;

if (Del_max = = 0)//this is a gray, no chroma ...
{
H = 2.0/3.0; Under Windows S value 0 o'clock, h value is always 160 (2/3*240)
H = 0; HSL results = 0÷1
S = 0;
}
Else//chromatic data ...
{
if (L < 0.5) S = Del_max/(Max + Min);
else S = Del_max/(2-max-min);

Del_r = (((max-r)/6.0) + (del_max/2.0))/Del_max;
Del_g = (((max-g)/6.0) + (del_max/2.0))/Del_max;
Del_b = (((max-b)/6.0) + (del_max/2.0))/Del_max;

if (R = = Max) H = Del_b-del_g;
else if (G = = Max) H = (1.0/3.0) + del_r-del_b;
else if (B = = Max) H = (2.0/3.0) + Del_g-del_r;

if (H < 0) H + = 1;
if (H > 1) H-= 1;
}
}

HSL conversion to RGB:
TColor Hsl2rgb (double h,double s,double L)
{
Double r,g,b;
Double var_1, var_2;
if (S = = 0)//HSL values = 0÷1
{
R = L * 255.0; RGB results = 0÷255
G = L * 255.0;
B = L * 255.0;
}
Else
{
if (L < 0.5) var_2 = L * (1 + S);
else var_2 = (L + s)-(S * l);

var_1 = 2.0 * l-var_2;

R = 255.0 * HUE2RGB (var_1, var_2, H + (1.0/3.0));
G = 255.0 * HUE2RGB (var_1, var_2, H);
B = 255.0 * HUE2RGB (var_1, var_2, H-(1.0/3.0));
}
Return TColor (RGB (r,g,b));
}
//---------------------------------------------------------------------------
Double Hue2rgb (Double v1, double v2, double VH)
{
if (VH < 0) VH + = 1;
if (VH > 1) VH-= 1;
if (6.0 * VH < 1) return v1 + (V2-V1) * 6.0 * VH;
if (2.0 * VH < 1) return v2;
if (3.0 * VH < 2) return v1 + (V2-V1) * ((2.0/3.0)-VH) * 6.0;
return (v1);
}

If you want to get the HSL value in Windows, you can overload these two functions and change the arguments to the int type:
#include <Math.hpp>

Convert RGB to HSL:
void RGB2HSL (TColor acolor, int &h,int &s,int &l)
{
Double h,s,l;
RGB2HSL (acolor,h,s,l);
h = roundto (h * 240,0);
s = roundto (S * 240,0);
L = roundto (L * 240,0);
}

HSL conversion to RGB:
TColor Hsl2rgb (int H, int S, int L)
{
Double h,s,l;
h = h/240.0;
s = s/240.0;
L = l/240.0;
Return Hsl2rgb (h,s,l);
}

Schedule (hsl/v/b in various environments):

applications	< P align= "Center" >space	H  range	S  range	l/v/b  range
Paint shop Pro	HSL	0-255	0-255	L	0-255
Gimp	< P align= "Center" >HSV	< Span style= "Font-size:small;" >0-360°	0-100	V	0-100
Photoshop	HSV	0-360°	0-100%	B	0-100%
Windows	HSL	0-240	0-240	L	0-240
Linux/kde	HSV	0-360°	0-255	V
GTK	< P align= "Center" >HSV	< Span style= "Font-size:small;" >0-360°	0-1.0	V	0-1.0
Java (AWT. Color)	HSV	0-1.0	0-1.0	B	0-1.0
Apple	Hsv	0-360°	0-100%	L	0-100%

Mutual conversion of RGB and HSL colors