Nits - Colorspaces (#880)

* Add missing periods

* Only perform matrix inversion once in CieXyzToLinearRgbConverter

* Eliminate unnessary ToVector3 call

* Seal GammaWorkingSpace

* Address stylecop violation

* Add periods

* Fix colorspace companding

Author: iamcarbon

src/ImageSharp/ColorSpaces/CieXyChromaticityCoordinates.cs

@@ -8,7 +8,7 @@
 namespace SixLabors.ImageSharp.ColorSpaces
 {
     /// <summary>
-    /// Represents the coordinates of CIEXY chromaticity space
+    /// Represents the coordinates of CIEXY chromaticity space.
     /// </summary>
     public readonly struct CieXyChromaticityCoordinates : IEquatable<CieXyChromaticityCoordinates>
     {

src/ImageSharp/ColorSpaces/Companding/GammaCompanding.cs

@@ -7,7 +7,7 @@
 namespace SixLabors.ImageSharp.ColorSpaces.Companding
 {
     /// <summary>
-    /// Implements gamma companding
+    /// Implements gamma companding.
     /// </summary>
     /// <remarks>
     /// <see href="http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html"/>

src/ImageSharp/ColorSpaces/Companding/LCompanding.cs

@@ -8,7 +8,7 @@
 namespace SixLabors.ImageSharp.ColorSpaces.Companding
 {
     /// <summary>
-    /// Implements L* companding
+    /// Implements L* companding.
     /// </summary>
     /// <remarks>
     /// For more info see:
@@ -24,7 +24,7 @@ public static class LCompanding
         /// <returns>The <see cref="float"/> representing the linear channel value.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public static float Expand(float channel)
-            => channel <= 0.08 ? 100 * channel / CieConstants.Kappa : ImageMaths.Pow3((channel + 0.16F) / 1.16F);
+            => channel <= 0.08F ? (100F * channel) / CieConstants.Kappa : ImageMaths.Pow3((channel + 0.16F) / 1.16F);
 
         /// <summary>
         /// Compresses an uncompanded channel (linear) to its nonlinear equivalent.
@@ -33,6 +33,6 @@ public static float Expand(float channel)
         /// <returns>The <see cref="float"/> representing the nonlinear channel value.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public static float Compress(float channel)
-            => channel <= CieConstants.Epsilon ? channel * CieConstants.Kappa / 100F : MathF.Pow(1.16F * channel, 0.3333333F) - 0.16F;
+            => channel <= CieConstants.Epsilon ? (channel * CieConstants.Kappa) / 100F : (1.16F * MathF.Pow(channel, 0.3333333F)) - 0.16F;
     }
 }

src/ImageSharp/ColorSpaces/Companding/Rec2020Companding.cs

@@ -7,22 +7,27 @@
 namespace SixLabors.ImageSharp.ColorSpaces.Companding
 {
     /// <summary>
-    /// Implements Rec. 2020 companding function (for 12-bits).
+    /// Implements Rec. 2020 companding function.
     /// </summary>
     /// <remarks>
     /// <see href="http://en.wikipedia.org/wiki/Rec._2020"/>
-    /// For 10-bits, companding is identical to <see cref="Rec709Companding"/>
     /// </remarks>
     public static class Rec2020Companding
     {
+        private const float Alpha = 1.09929682680944F;
+        private const float AlphaMinusOne = Alpha - 1F;
+        private const float Beta = 0.018053968510807F;
+        private const float InverseBeta = Beta * 4.5F;
+        private const float Epsilon = 1 / 0.45F;
+
         /// <summary>
         /// Expands a companded channel to its linear equivalent with respect to the energy.
         /// </summary>
         /// <param name="channel">The channel value.</param>
         /// <returns>The <see cref="float"/> representing the linear channel value.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public static float Expand(float channel)
-            => channel < 0.08145F ? channel / 4.5F : MathF.Pow((channel + 0.0993F) / 1.0993F, 2.222222F);
+            => channel < InverseBeta ? channel / 4.5F : MathF.Pow((channel + AlphaMinusOne) / Alpha, Epsilon);
 
         /// <summary>
         /// Compresses an uncompanded channel (linear) to its nonlinear equivalent.
@@ -31,6 +36,6 @@ public static float Expand(float channel)
         /// <returns>The <see cref="float"/> representing the nonlinear channel value.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public static float Compress(float channel)
-            => channel < 0.0181F ? 4500F * channel : (1.0993F * channel) - 0.0993F;
+            => channel < Beta ? 4.5F * channel : (Alpha * MathF.Pow(channel, 0.45F)) - AlphaMinusOne;
     }
 }

src/ImageSharp/ColorSpaces/Companding/Rec709Companding.cs

@@ -14,14 +14,16 @@ namespace SixLabors.ImageSharp.ColorSpaces.Companding
     /// </remarks>
     public static class Rec709Companding
     {
+        private const float Epsilon = 1 / 0.45F;
+
         /// <summary>
         /// Expands a companded channel to its linear equivalent with respect to the energy.
         /// </summary>
         /// <param name="channel">The channel value.</param>
         /// <returns>The <see cref="float"/> representing the linear channel value.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public static float Expand(float channel)
-            => channel < 0.081F ? channel / 4.5F : MathF.Pow((channel + 0.099F) / 1.099F, 2.222222F);
+            => channel < 0.081F ? channel / 4.5F : MathF.Pow((channel + 0.099F) / 1.099F, Epsilon);
 
         /// <summary>
         /// Compresses an uncompanded channel (linear) to its nonlinear equivalent.
@@ -30,6 +32,6 @@ public static float Expand(float channel)
         /// <returns>The <see cref="float"/> representing the nonlinear channel value.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public static float Compress(float channel)
-            => channel < 0.018F ? 4500F * channel : (1.099F * channel) - 0.099F;
+            => channel < 0.018F ? 4.5F * channel : (1.099F * MathF.Pow(channel, 0.45F)) - 0.099F;
     }
 }

src/ImageSharp/ColorSpaces/Conversion/ColorSpaceConverter.CieLch.cs

@@ -26,10 +26,8 @@ public partial class ColorSpaceConverter
         /// <returns>The <see cref="CieLch"/></returns>
         public CieLch ToCieLch(in CieLab color)
         {
-            // Adaptation
             CieLab adapted = this.Adapt(color);
 
-            // Conversion
             return CieLabToCieLchConverter.Convert(adapted);
         }
 

src/ImageSharp/ColorSpaces/Conversion/Implementation/Converters/CieXyzAndCieXyyConverter.cs

@@ -7,7 +7,7 @@
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation
 {
     /// <summary>
-    /// Color converter between CIE XYZ and CIE xyY
+    /// Color converter between CIE XYZ and CIE xyY.
     /// <see href="http://www.brucelindbloom.com/"/> for formulas.
     /// </summary>
     internal sealed class CieXyzAndCieXyyConverter

src/ImageSharp/ColorSpaces/Conversion/Implementation/Converters/CieXyzToLinearRgbConverter.cs

@@ -28,24 +28,28 @@ public CieXyzToLinearRgbConverter()
         public CieXyzToLinearRgbConverter(RgbWorkingSpaceBase workingSpace)
         {
             this.TargetWorkingSpace = workingSpace;
-            this.conversionMatrix = GetRgbToCieXyzMatrix(workingSpace);
+
+            // Gets the inverted Rgb -> Xyz matrix
+            Matrix4x4.Invert(GetRgbToCieXyzMatrix(workingSpace), out Matrix4x4 inverted);
+
+            this.conversionMatrix = inverted;
         }
 
         /// <summary>
-        /// Gets the target working space
+        /// Gets the target working space.
         /// </summary>
         public RgbWorkingSpaceBase TargetWorkingSpace { get; }
 
         /// <summary>
         /// Performs the conversion from the <see cref="CieXyz"/> input to an instance of <see cref="LinearRgb"/> type.
         /// </summary>
         /// <param name="input">The input color instance.</param>
-        /// <returns>The converted result</returns>
+        /// <returns>The converted result.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public LinearRgb Convert(in CieXyz input)
         {
-            Matrix4x4.Invert(this.conversionMatrix, out Matrix4x4 inverted);
-            var vector = Vector3.Transform(input.ToVector3(), inverted);
+            var vector = Vector3.Transform(input.ToVector3(), this.conversionMatrix);
+
             return new LinearRgb(vector, this.TargetWorkingSpace);
         }
     }

src/ImageSharp/ColorSpaces/Conversion/Implementation/Converters/CmykAndRgbConverter.cs

@@ -8,7 +8,7 @@
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation
 {
     /// <summary>
-    /// Color converter between <see cref="Cmyk"/> and <see cref="Rgb"/>
+    /// Color converter between <see cref="Cmyk"/> and <see cref="Rgb"/>.
     /// </summary>
     internal sealed class CmykAndRgbConverter
     {
@@ -28,7 +28,7 @@ public Rgb Convert(in Cmyk input)
         /// Performs the conversion from the <see cref="Rgb"/> input to an instance of <see cref="Cmyk"/> type.
         /// </summary>
         /// <param name="input">The input color instance.</param>
-        /// <returns>The converted result</returns>
+        /// <returns>The converted result.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public Cmyk Convert(in Rgb input)
         {

src/ImageSharp/ColorSpaces/Conversion/Implementation/Converters/LinearRgbToRgbConverter.cs

@@ -6,24 +6,23 @@
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation
 {
     /// <summary>
-    /// Color converter between <see cref="LinearRgb"/> and <see cref="Rgb"/>
+    /// Color converter between <see cref="LinearRgb"/> and <see cref="Rgb"/>.
     /// </summary>
     internal sealed class LinearRgbToRgbConverter
     {
         /// <summary>
         /// Performs the conversion from the <see cref="LinearRgb"/> input to an instance of <see cref="Rgb"/> type.
         /// </summary>
         /// <param name="input">The input color instance.</param>
-        /// <returns>The converted result</returns>
+        /// <returns>The converted result.</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public Rgb Convert(in LinearRgb input)
         {
-            var vector = input.ToVector3();
-            vector.X = input.WorkingSpace.Compress(vector.X);
-            vector.Y = input.WorkingSpace.Compress(vector.Y);
-            vector.Z = input.WorkingSpace.Compress(vector.Z);
-
-            return new Rgb(vector, input.WorkingSpace);
+            return new Rgb(
+                r: input.WorkingSpace.Compress(input.R),
+                g: input.WorkingSpace.Compress(input.G),
+                b: input.WorkingSpace.Compress(input.B),
+                workingSpace: input.WorkingSpace);
         }
     }
 }