Added CCT computation

Author: castarco

ColorSharp/src/ColorSpaces/AConvertibleColor.cs

@@ -28,7 +28,8 @@
 
 
 using System;
-using System.Collections.Generic;
+
+using Litipk.ColorSharp.LightSpectrums;
 
 
 namespace Litipk.ColorSharp
@@ -124,6 +125,18 @@ AConvertibleColor InnerConvertTo (Type t, ColorStrategy strategy = ColorStrategy
 			 */
 			public abstract bool IsInsideColorSpace (bool highPrecision = false);
 
+			/**
+			 * <summary>Gives us the Correlater Color Temperature associated to the spectrum or color.</summary>
+			 */
+			public virtual double GetCCT ()
+			{
+				if (DataSource is BlackBodySpectrum) {
+					return DataSource.GetCCT ();
+				}
+
+				return ToCIEUCS ().GetCCT ();
+			}
+
 			/**
 			 * <summary>Converts the color sample to a CIE's 1931 XYZ color sample.</summary>
 			 */

ColorSharp/src/ColorSpaces/CIEUCS.cs

@@ -28,6 +28,9 @@
 
 
 using System;
+using System.Collections.Generic;
+
+using Litipk.ColorSharp.LightSpectrums;
 
 
 namespace Litipk.ColorSharp
@@ -74,6 +77,8 @@ public sealed class CIEUCS : AConvertibleColor
 			 */
 			public double Y { get { return V; } }
 
+			static List<CIEUCS> TemperatureChromaticities = null;
+
 			#endregion
 
 
@@ -146,10 +151,10 @@ public CIEUCS (double U, double V, double u, double v, double W, AConvertibleCol
 					throw new ArgumentException ("Invalid color point");
 				}
 
-				if (Math.Abs (U / (U + V + W) - u) > 8*double.Epsilon) {
+				if (Math.Abs (U / (U + V + W) - u) > 1e-15) {
 					throw new ArgumentException ("Inconsistent data");
 				}
-				if (Math.Abs (V / (U + V + W) - v) > 8*double.Epsilon) {
+				if (Math.Abs (V / (U + V + W) - v) > 1e-15) {
 					throw new ArgumentException ("Inconsistent data");
 				}
 
@@ -177,6 +182,66 @@ public override bool IsInsideColorSpace(bool highPrecision = false)
 				return ToCIExyY ().IsInsideColorSpace (highPrecision);
 			}
 
+			public override double GetCCT ()
+			{
+				if (DataSource is BlackBodySpectrum) {
+					return (DataSource as BlackBodySpectrum).CCT;
+				}
+
+				if (TemperatureChromaticities == null) {
+					// Oversized to improve alignment (needs 302).
+					TemperatureChromaticities = new List<CIEUCS> (512);
+
+					// From 1000º K to 20000º K
+					for (double t = 1000.0; t < 20001.0; t *= 1.01) {
+						TemperatureChromaticities.Add (
+							new BlackBodySpectrum (t).ToCIEXYZ (SpectrumStrategy.Nm1Deg2).ToCIEUCS ()
+						);
+					}
+				}
+
+				int bestI = 0;
+				double minDuv = double.PositiveInfinity;
+
+				// First gross grained search
+				// TODO: This is a naive search, must be improved!
+				for (int i = 0; i < TemperatureChromaticities.Count; i++) {
+					double tmpDuv = Math.Sqrt (
+		                Math.Pow (u - TemperatureChromaticities [i].u, 2) +
+		                Math.Pow (v - TemperatureChromaticities [i].v, 2)
+	                );
+
+					if (minDuv > tmpDuv) {
+						minDuv = tmpDuv;
+						bestI = i;
+					}
+				}
+				double bestTmp = TemperatureChromaticities [bestI].GetCCT ();
+
+				// Preparing the following fine grained search
+				double tMin = TemperatureChromaticities [
+					(bestI > 0) ? bestI - 1 : bestI
+				].GetCCT ();
+				double tMax = TemperatureChromaticities [
+					(bestI < TemperatureChromaticities.Count - 1) ? bestI + 1 : bestI
+				].GetCCT ();
+				double tDiff = (tMax - tMin) / 100.0;
+
+				// Second fine grained search
+				for (double t = tMin; t < tMax; t += tDiff) {
+					var tmpUV = new BlackBodySpectrum (t).ToCIEXYZ (SpectrumStrategy.Nm1Deg2).ToCIEUCS ();
+
+					double tmpDuv = Math.Sqrt (Math.Pow (u - tmpUV.u, 2) +	Math.Pow (v - tmpUV.v, 2));
+
+					if (minDuv > tmpDuv) {
+						minDuv = tmpDuv;
+						bestTmp = t;
+					}
+				}
+
+				return bestTmp;
+			}
+
 			/**
 			 * <inheritdoc />
 			 */

ColorSharp/src/ColorSpaces/CIExyY.cs

@@ -190,6 +190,30 @@ public override CIExyY ToCIExyY (ColorStrategy strategy = ColorStrategy.Default)
 				return this;
 			}
 
+			/**
+			 * <inheritdoc />
+			 */
+			public override CIEUCS ToCIEUCS (ColorStrategy strategy = ColorStrategy.Default)
+			{
+				if (DataSource is CIEUCS) {
+					return DataSource as CIEUCS;
+				}
+
+				// Warning, it's not a good idea to do it with other types, we do with CIEXYZ bacause
+				// we have a more precise conversion and because a call-loop it's not possible.
+				if (DataSource is CIEXYZ) {
+					return (DataSource as CIEXYZ).ToCIEUCS ();
+				}
+
+				double div = (12 * y - 2 * x + 3);
+				double yy = Y / y;
+
+				return new CIEUCS (
+					DataSource ?? this,
+					4 * x / div, 6 * y / div, 0.5 * (-x * yy + 3 * Y + yy * (1.0 - x - y))
+				);
+			}
+
 			#endregion
 
 

ColorSharp/src/LightSpectrums/ALightSpectrum.cs

@@ -132,7 +132,7 @@ public CIEXYZ ToCIEXYZ (SpectrumStrategy strategy=SpectrumStrategy.Default)
 					Z += MFs [2].EvaluateAt (i * step + minV) * v * step;
 				}
 
-				return new CIEXYZ (X, Y, Z);
+				return new CIEXYZ (X, Y, Z, DataSource ?? this);
 			}
 
 			#endregion

ColorSharp/src/LightSpectrums/BlackBodySpectrum.cs

@@ -113,6 +113,14 @@ public override bool IsInsideColorSpace (bool highPrecision = false)
 				return true;
 			}
 
+			/**
+			 * <inheritdoc />
+			 */
+			public override double GetCCT ()
+			{
+				return CCT;
+			}
+
 			#endregion
 		}
 	}

ColorSharp/src/LightSpectrums/RegularLightSpectrum.cs

@@ -33,7 +33,6 @@
 using System.Collections.ObjectModel;
 
 using Litipk.ColorSharp.ColorSpaces;
-using Litipk.ColorSharp.InternalUtils;
 
 
 namespace Litipk.ColorSharp