/// <summary>
/// Converts a colour from HSL to RGB
/// </summary>
/// <remarks>Adapted from the algoritm in Foley and Van-Dam</remarks>
/// <param name="hsl">The HSL value</param>
/// <returns>A Color structure containing the equivalent RGB values</returns>
public static Color HSL_to_RGB(HSL hsl)
{
int Max, Mid, Min;
double q;
Max = Round(hsl.L * 255);
Min = Round((1.0 - hsl.S) * (hsl.L / 1.0) * 255);
q = (double)(Max - Min) / 255;
if (hsl.H >= 0 && hsl.H <= (double)1 / 6)
{
Mid = Round(((hsl.H - 0) * q) * 1530 + Min);
return(Color.FromArgb(Max, Mid, Min));
}
else if (hsl.H <= (double)1 / 3)
{
Mid = Round(-((hsl.H - (double)1 / 6) * q) * 1530 + Max);
return(Color.FromArgb(Mid, Max, Min));
}
else if (hsl.H <= 0.5)
{
Mid = Round(((hsl.H - (double)1 / 3) * q) * 1530 + Min);
return(Color.FromArgb(Min, Max, Mid));
}
else if (hsl.H <= (double)2 / 3)
{
Mid = Round(-((hsl.H - 0.5) * q) * 1530 + Max);
return(Color.FromArgb(Min, Mid, Max));
}
else if (hsl.H <= (double)5 / 6)
{
Mid = Round(((hsl.H - (double)2 / 3) * q) * 1530 + Min);
return(Color.FromArgb(Mid, Min, Max));
}
else if (hsl.H <= 1.0)
{
Mid = Round(-((hsl.H - (double)5 / 6) * q) * 1530 + Max);
return(Color.FromArgb(Max, Min, Mid));
}
else
{
return(Color.FromArgb(0, 0, 0));
}
}
/// <summary>
/// Converts RGB to HSL
/// </summary>
/// <remarks>Takes advantage of whats already built in to .NET by using the Color.GetHue, Color.GetSaturation and Color.GetBrightness methods</remarks>
/// <param name="c">A Color to convert</param>
/// <returns>An HSL value</returns>
public static HSL RGB_to_HSL(Color c)
{
HSL hsl = new HSL();
int Max, Min, Diff, Sum;
// Of our RGB values, assign the highest value to Max, and the Smallest to Min
if (c.R > c.G)
{
Max = c.R; Min = c.G;
}
else
{
Max = c.G; Min = c.R;
}
if (c.B > Max)
{
Max = c.B;
}
else if (c.B < Min)
{
Min = c.B;
}
Diff = Max - Min;
Sum = Max + Min;
// Luminance - a.k.a. Brightness - Adobe photoshop uses the logic that the
// site VBspeed regards (regarded) as too primitive = superior decides the
// level of brightness.
hsl.L = (double)Max / 255;
// Saturation
if (Max == 0)
{
hsl.S = 0; // Protecting from the impossible operation of division by zero.
}
else
{
hsl.S = (double)Diff / Max; // The logic of Adobe Photoshops is this simple.
}
// Hue R is situated at the angel of 360 eller noll degrees;
// G vid 120 degrees
// B vid 240 degrees
double q;
if (Diff == 0)
{
q = 0; // Protecting from the impossible operation of division by zero.
}
else
{
q = (double)60 / Diff;
}
if (Max == c.R)
{
if (c.G < c.B)
{
hsl.H = (double)(360 + q * (c.G - c.B)) / 360;
}
else
{
hsl.H = (double)(q * (c.G - c.B)) / 360;
}
}
else if (Max == c.G)
{
hsl.H = (double)(120 + q * (c.B - c.R)) / 360;
}
else if (Max == c.B)
{
hsl.H = (double)(240 + q * (c.R - c.G)) / 360;
}
else
{
hsl.H = 0.0;
}
return(hsl);
}
