/// <summary>Gets the saturation value, in percentages, for this <see cref="T:Licorne.Rgb" /> structure.</summary>
/// <returns>The saturation, in percentages, of this <see cref="T:Licorne.Rgb" />. The saturation is measured in percentages, ranging from 0.0 through 100.0, in HSL color space.</returns>
/// <param name="rgb">The <see cref="T:Licorne.Rgb" /> from which to get the saturation.</param>
private static double GetSaturation(Rgb rgb)
{
const int greySaturation = 0;
var r = rgb.R / 255d;
var g = rgb.G / 255d;
var b = rgb.B / 255d;
var max = r;
var min = r;
if (g > max)
{
max = g;
}
if (b > max)
{
max = b;
}
if (g < min)
{
min = g;
}
if (b < min)
{
min = b;
}
// if max == min, then there is no color and
// the saturation is zero.
if (max.BasicallyEqualTo(min))
{
return(greySaturation);
}
var l = (max + min) / 2;
var s = (max - min) / (l <= .5 ? max + min : (2 - max - min)); // double
return(s);
}
/// <summary>Creates a <see cref="T:Licorne.Hsl" /> structure from the specified <see cref="T:Licorne.Rgb" /> structure.</summary>
/// <returns>The <see cref="T:Licorne.Hsl" /> that this method creates.</returns>
/// <param name="color">The <see cref="T:Licorne.Rgb" /> from which to create the new <see cref="T:Licorne.Hsl" />.</param>
public Hsl(Rgb color) : this(GetHue(color)
, GetSaturation(color) * 100d
, GetLuminosity(color) * 100d)
{
}
/// <summary>Gets the hue value, in degrees, for this <see cref="T:Licorne.Rgb" /> structure.</summary>
/// <returns>The hue, in degrees, of this <see cref="T:Licorne.Rgb" />. The hue is measured in degrees, ranging from 0.0 through 360.0, in HSL color space.</returns>
/// <param name="rgb">The <see cref="T:Licorne.Rgb" /> from which to get the hue.</param>
private static double GetHue(Rgb rgb)
{
// 0 makes as good an UNDEFINED value as any
const int greyHue = 0;
if (rgb.R.BasicallyEqualTo(rgb.G) && rgb.G.BasicallyEqualTo(rgb.B))
{
return(greyHue);
}
var r = rgb.R / 255d;
var g = rgb.G / 255d;
var b = rgb.B / 255d;
double max, min;
double delta;
var hue = 0d;
max = r;
min = r;
if (g > max)
{
max = g;
}
if (b > max)
{
max = b;
}
if (g < min)
{
min = g;
}
if (b < min)
{
min = b;
}
delta = max - min;
if (r.BasicallyEqualTo(max))
{
hue = 0 + (g - b) / delta;
}
else if (g.BasicallyEqualTo(max))
{
hue = 2 + (b - r) / delta;
}
else if (b.BasicallyEqualTo(max))
{
hue = 4 + (r - g) / delta;
}
hue *= 60;
if (hue < 0d)
{
hue += 360d;
}
return(hue);
}