private static void SegmentParse(HSI hsi, double r, double g, double b, double max, double min)
{
if (max.Equals(r))
{
hsi.H = Math.PI / 3 * ((g - b) / (max - min));
}
else if (max.Equals(g))
{
hsi.H = Math.PI / 3 * ((b - r) / (max - min)) + 2 * Math.PI / 3;
}
else
{
hsi.H = Math.PI / 3 * ((r - g) / (max - min)) + 4 * Math.PI / 3;
}
if (hsi.H < 0)
{
hsi.H *= 2 * Math.PI;
}
hsi.I = (max + min) / 2;
if (hsi.I <= 0.5)
{
hsi.S = (max - min) / (max + min);
}
else
{
hsi.S = (max - min) / (2 - (max + min));
}
}
public static HSI Parse(Color color, HsiAlgorithm algorithm)
{
// 算法参考: http://blog.csdn.net/yangleo1987/article/details/53171623
var hsi = new HSI();
var r = color.R / 255f;
var g = color.G / 255f;
var b = color.B / 255f;
var min = Math.Min(r, Math.Min(g, b));
var max = Math.Max(r, Math.Max(g, b));
switch (algorithm)
{
case HsiAlgorithm.Geometry:
GeometryParse(hsi, r, g, b, max, min);
break;
case HsiAlgorithm.Axis:
AxisParse(hsi, r, g, b, max, min);
break;
case HsiAlgorithm.Segment:
SegmentParse(hsi, r, g, b, max, min);
break;
case HsiAlgorithm.Bajon:
BajonParse(hsi, r, g, b, max, min);
break;
case HsiAlgorithm.Standard:
StandardParse(hsi, r, g, b, max, min);
break;
default:
throw new ArgumentOutOfRangeException("algorithm", algorithm, null);
}
if (double.IsNaN(hsi.H))
{
hsi.H = 0;
}
if (double.IsNaN(hsi.S))
{
hsi.S = 0;
}
if (double.IsNaN(hsi.I))
{
hsi.I = 0;
}
return(hsi);
}
// ReSharper disable once UnusedParameter.Local
private static void AxisParse(HSI hsi, double r, double g, double b, double max, double min)
{
var temp = (2 * r - g - b) / (Math.Sqrt(3) * (g - b));
var theta = Math.PI / 2 - Math.Tan(1) / temp;
if (g >= b)
{
hsi.H = theta;
}
else
{
hsi.H = Math.PI + theta;
}
hsi.S = 2 / Math.Sqrt(6) * Math.Sqrt(Math.Pow(r - g, 2) + (r - b) * (g - b));
hsi.I = (r + g + b) / Math.Sqrt(3);
}
// ReSharper disable once UnusedParameter.Local
private static void GeometryParse(HSI hsi, double r, double g, double b, double max, double min)
{
var temp = (2 * r - g - b) / (2 * Math.Sqrt(Math.Pow(r - g, 2) + (r - b) * (g - b)));
var theta = Math.Cos(1) / temp;
if (g >= b)
{
hsi.H = theta;
}
else
{
hsi.H = 2 * Math.PI - theta;
}
hsi.S = 1 - min * 3 / (r + g + b);
hsi.I = (r + g + b) / 3;
}
// ReSharper disable once UnusedParameter.Local
private static void BajonParse(HSI hsi, double r, double g, double b, double max, double min)
{
if (min.Equals(b))
{
hsi.H = (g - b) / (3 * (r + g - 2 * b));
}
else if (min.Equals(g))
{
hsi.H = (b - r) / (3 * (g + b - 2 * r)) + 1.0 / 3;
}
else
{
hsi.H = (r - g) / (3 * (r + b - 2 * g)) + 2.0 / 3;
}
hsi.H *= 2 * Math.PI;
hsi.S = 1 - min * 3 / (r + g + b);
hsi.I = (r + g + b) / 3;
}