Merge ab7effe1c5 into 59ce6af6fc

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsCieLabCieLab.cs

@@ -41,7 +41,7 @@ public static class ColorProfileConverterExtensionsCieLabCieLab
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix);
+        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS
         CieLab pcsTo = CieLab.FromProfileConnectingSpace(options, in pcsFromB);
@@ -87,7 +87,7 @@ public static class ColorProfileConverterExtensionsCieLabCieLab
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS.
         CieLab.FromProfileConnectionSpace(options, pcsFrom, pcsFromTo);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsCieLabCieXyz.cs

@@ -43,7 +43,7 @@ public static class ColorProfileConverterExtensionsCieLabCieXyz
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsTo = VonKriesChromaticAdaptation.Transform(in pcsTo, whitePoints, options.AdaptationMatrix);
+        pcsTo = VonKriesChromaticAdaptation.Transform(in pcsTo, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert to output from PCS
         return TTo.FromProfileConnectingSpace(options, in pcsTo);
@@ -87,7 +87,7 @@ public static class ColorProfileConverterExtensionsCieLabCieXyz
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsTo, pcsTo, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsTo, pcsTo, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert to output from PCS
         TTo.FromProfileConnectionSpace(options, pcsTo, destination);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsCieLabRgb.cs

@@ -41,7 +41,7 @@ public static class ColorProfileConverterExtensionsCieLabRgb
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix);
+        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS
         Rgb pcsTo = Rgb.FromProfileConnectingSpace(options, in pcsFromB);
@@ -87,7 +87,7 @@ public static class ColorProfileConverterExtensionsCieLabRgb
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFromB, pcsFromB, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFromB, pcsFromB, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS.
         using IMemoryOwner<Rgb> pcsToOwner = options.MemoryAllocator.Allocate<Rgb>(source.Length);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsCieXyzCieLab.cs

@@ -40,7 +40,7 @@ public static class ColorProfileConverterExtensionsCieXyzCieLab
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFrom = VonKriesChromaticAdaptation.Transform(in pcsFrom, whitePoints, options.AdaptationMatrix);
+        pcsFrom = VonKriesChromaticAdaptation.Transform(in pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS
         CieLab pcsTo = CieLab.FromProfileConnectingSpace(options, in pcsFrom);
@@ -82,7 +82,7 @@ public static class ColorProfileConverterExtensionsCieXyzCieLab
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS.
         using IMemoryOwner<CieLab> pcsToOwner = options.MemoryAllocator.Allocate<CieLab>(source.Length);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsCieXyzCieXyz.cs

@@ -40,7 +40,7 @@ public static class ColorProfileConverterExtensionsCieXyzCieXyz
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFrom = VonKriesChromaticAdaptation.Transform(in pcsFrom, whitePoints, options.AdaptationMatrix);
+        pcsFrom = VonKriesChromaticAdaptation.Transform(in pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert to output from PCS
         return TTo.FromProfileConnectingSpace(options, in pcsFrom);
@@ -79,7 +79,7 @@ public static class ColorProfileConverterExtensionsCieXyzCieXyz
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert to output from PCS
         TTo.FromProfileConnectionSpace(options, pcsFrom, destination);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsCieXyzRgb.cs

@@ -40,7 +40,7 @@ public static class ColorProfileConverterExtensionsCieXyzRgb
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFrom = VonKriesChromaticAdaptation.Transform(in pcsFrom, whitePoints, options.AdaptationMatrix);
+        pcsFrom = VonKriesChromaticAdaptation.Transform(in pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS
         Rgb pcsTo = Rgb.FromProfileConnectingSpace(options, in pcsFrom);
@@ -82,7 +82,7 @@ public static class ColorProfileConverterExtensionsCieXyzRgb
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS.
         using IMemoryOwner<Rgb> pcsToOwner = options.MemoryAllocator.Allocate<Rgb>(source.Length);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsRgbCieLab.cs

@@ -41,7 +41,7 @@ public static class ColorProfileConverterExtensionsRgbCieLab
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix);
+        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS
         CieLab pcsTo = CieLab.FromProfileConnectingSpace(options, in pcsFromB);
@@ -87,7 +87,7 @@ public static class ColorProfileConverterExtensionsRgbCieLab
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFromB, pcsFromB, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFromB, pcsFromB, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS.
         using IMemoryOwner<CieLab> pcsToOwner = options.MemoryAllocator.Allocate<CieLab>(source.Length);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsRgbCieXyz.cs

@@ -43,7 +43,7 @@ public static class ColorProfileConverterExtensionsRgbCieXyz
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsTo = VonKriesChromaticAdaptation.Transform(in pcsTo, whitePoints, options.AdaptationMatrix);
+        pcsTo = VonKriesChromaticAdaptation.Transform(in pcsTo, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert to output from PCS
         return TTo.FromProfileConnectingSpace(options, in pcsTo);
@@ -87,7 +87,7 @@ public static class ColorProfileConverterExtensionsRgbCieXyz
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsTo, pcsTo, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsTo, pcsTo, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert to output from PCS
         TTo.FromProfileConnectionSpace(options, pcsTo, destination);

src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsRgbRgb.cs

@@ -41,7 +41,7 @@ public static class ColorProfileConverterExtensionsRgbRgb
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix);
+        pcsFromB = VonKriesChromaticAdaptation.Transform(in pcsFromB, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS
         Rgb pcsTo = Rgb.FromProfileConnectingSpace(options, in pcsFromB);
@@ -87,7 +87,7 @@ public static class ColorProfileConverterExtensionsRgbRgb
 
         // Adapt to target white point
         (CieXyz From, CieXyz To) whitePoints = converter.GetChromaticAdaptionWhitePoints<TFrom, TTo>();
-        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix);
+        VonKriesChromaticAdaptation.Transform(pcsFrom, pcsFrom, whitePoints, options.AdaptationMatrix, options.InverseAdaptationMatrix);
 
         // Convert between PCS.
         Rgb.FromProfileConnectionSpace(options, pcsFrom, pcsFromTo);

src/ImageSharp/ColorProfiles/Rgb.cs

@@ -272,7 +272,7 @@ public readonly struct Rgb : IProfileConnectingSpace<Rgb, CieXyz>
     public static Rgb FromProfileConnectingSpace(ColorConversionOptions options, in CieXyz source)
     {
         // Convert to linear rgb then compress.
-        Rgb linear = new(Vector3.Transform(source.AsVector3Unsafe(), GetCieXyzToRgbMatrix(options.TargetRgbWorkingSpace)));
+        Rgb linear = new(Vector3.Transform(source.AsVector3Unsafe(), options.TargetRgbWorkingSpace.CieXyzToRgbMatrix));
         return FromScaledVector4(options.TargetRgbWorkingSpace.Compress(linear.ToScaledVector4()));
     }
 
@@ -281,7 +281,7 @@ public readonly struct Rgb : IProfileConnectingSpace<Rgb, CieXyz>
     {
         Guard.DestinationShouldNotBeTooShort(source, destination, nameof(destination));
 
-        Matrix4x4 matrix = GetCieXyzToRgbMatrix(options.TargetRgbWorkingSpace);
+        Matrix4x4 matrix = options.TargetRgbWorkingSpace.CieXyzToRgbMatrix;
         for (int i = 0; i < source.Length; i++)
         {
             // Convert to linear rgb then compress.
@@ -298,7 +298,7 @@ public readonly struct Rgb : IProfileConnectingSpace<Rgb, CieXyz>
         Rgb linear = FromScaledVector4(options.SourceRgbWorkingSpace.Expand(this.ToScaledVector4()));
 
         // Then convert to xyz
-        return new CieXyz(Vector3.Transform(linear.AsVector3Unsafe(), GetRgbToCieXyzMatrix(options.SourceRgbWorkingSpace)));
+        return new CieXyz(Vector3.Transform(linear.AsVector3Unsafe(), options.SourceRgbWorkingSpace.RgbToCieXyzMatrix));
     }
 
     /// <inheritdoc/>
@@ -306,7 +306,7 @@ public readonly struct Rgb : IProfileConnectingSpace<Rgb, CieXyz>
     {
         Guard.DestinationShouldNotBeTooShort(source, destination, nameof(destination));
 
-        Matrix4x4 matrix = GetRgbToCieXyzMatrix(options.SourceRgbWorkingSpace);
+        Matrix4x4 matrix = options.SourceRgbWorkingSpace.RgbToCieXyzMatrix;
         for (int i = 0; i < source.Length; i++)
         {
             Rgb rgb = source[i];
@@ -371,68 +371,6 @@ public readonly struct Rgb : IProfileConnectingSpace<Rgb, CieXyz>
 
     internal Vector3 AsVector3Unsafe() => Unsafe.As<Rgb, Vector3>(ref Unsafe.AsRef(in this));
 
-    private static Matrix4x4 GetCieXyzToRgbMatrix(RgbWorkingSpace workingSpace)
-    {
-        Matrix4x4 matrix = GetRgbToCieXyzMatrix(workingSpace);
-        Matrix4x4.Invert(matrix, out Matrix4x4 inverseMatrix);
-        return inverseMatrix;
-    }
-
-    private static Matrix4x4 GetRgbToCieXyzMatrix(RgbWorkingSpace workingSpace)
-    {
-        DebugGuard.NotNull(workingSpace, nameof(workingSpace));
-        RgbPrimariesChromaticityCoordinates chromaticity = workingSpace.ChromaticityCoordinates;
-
-        float xr = chromaticity.R.X;
-        float xg = chromaticity.G.X;
-        float xb = chromaticity.B.X;
-        float yr = chromaticity.R.Y;
-        float yg = chromaticity.G.Y;
-        float yb = chromaticity.B.Y;
-
-        float mXr = xr / yr;
-        float mZr = (1 - xr - yr) / yr;
-
-        float mXg = xg / yg;
-        float mZg = (1 - xg - yg) / yg;
-
-        float mXb = xb / yb;
-        float mZb = (1 - xb - yb) / yb;
-
-        Matrix4x4 xyzMatrix = new()
-        {
-            M11 = mXr,
-            M21 = mXg,
-            M31 = mXb,
-            M12 = 1F,
-            M22 = 1F,
-            M32 = 1F,
-            M13 = mZr,
-            M23 = mZg,
-            M33 = mZb,
-            M44 = 1F
-        };
-
-        Matrix4x4.Invert(xyzMatrix, out Matrix4x4 inverseXyzMatrix);
-
-        Vector3 vector = Vector3.Transform(workingSpace.WhitePoint.AsVector3Unsafe(), inverseXyzMatrix);
-
-        // Use transposed Rows/Columns
-        return new Matrix4x4
-        {
-            M11 = vector.X * mXr,
-            M21 = vector.Y * mXg,
-            M31 = vector.Z * mXb,
-            M12 = vector.X,
-            M22 = vector.Y,
-            M32 = vector.Z,
-            M13 = vector.X * mZr,
-            M23 = vector.Y * mZg,
-            M33 = vector.Z * mZb,
-            M44 = 1F
-        };
-    }
-
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static Vector512<float> ReadVector512(ref float src)
     {

src/ImageSharp/ColorProfiles/VonKriesChromaticAdaptation.cs

@@ -25,6 +25,47 @@ public static class VonKriesChromaticAdaptation
     /// <param name="matrix">The chromatic adaptation matrix.</param>
     /// <returns>The <see cref="CieXyz"/></returns>
     public static CieXyz Transform(in CieXyz source, (CieXyz From, CieXyz To) whitePoints, Matrix4x4 matrix)
+    {
+        Matrix4x4.Invert(matrix, out Matrix4x4 inverseMatrix);
+        return Transform(in source, whitePoints, matrix, inverseMatrix);
+    }
+
+    /// <summary>
+    /// Performs a bulk linear transformation of a source color in to the destination color.
+    /// </summary>
+    /// <remarks>Doesn't crop the resulting color space coordinates (e. g. allows negative values for XYZ coordinates).</remarks>
+    /// <param name="source">The span to the source colors.</param>
+    /// <param name="destination">The span to the destination colors.</param>
+    /// <param name="whitePoints">The conversion white points.</param>
+    /// <param name="matrix">The chromatic adaptation matrix.</param>
+    public static void Transform(
+        ReadOnlySpan<CieXyz> source,
+        Span<CieXyz> destination,
+        (CieXyz From, CieXyz To) whitePoints,
+        Matrix4x4 matrix)
+    {
+        Matrix4x4.Invert(matrix, out Matrix4x4 inverseMatrix);
+        Transform(source, destination, whitePoints, matrix, inverseMatrix);
+    }
+
+    /// <summary>
+    /// Performs a linear transformation of a source color in to the destination color using a
+    /// precomputed inverse of <paramref name="matrix"/>.
+    /// </summary>
+    /// <remarks>
+    /// For callers that already hold the inverse, e.g. <see cref="ColorConversionOptions.InverseAdaptationMatrix"/>,
+    /// to avoid repeating <see cref="Matrix4x4.Invert"/> on every call.
+    /// </remarks>
+    /// <param name="source">The source color.</param>
+    /// <param name="whitePoints">The conversion white points.</param>
+    /// <param name="matrix">The chromatic adaptation matrix.</param>
+    /// <param name="inverseMatrix">The inverse of <paramref name="matrix"/>.</param>
+    /// <returns>The <see cref="CieXyz"/></returns>
+    internal static CieXyz Transform(
+        in CieXyz source,
+        (CieXyz From, CieXyz To) whitePoints,
+        Matrix4x4 matrix,
+        Matrix4x4 inverseMatrix)
     {
         CieXyz from = whitePoints.From;
         CieXyz to = whitePoints.To;
@@ -41,23 +82,28 @@ public static class VonKriesChromaticAdaptation
         Vector3 vector = targetWhitePointLms / sourceWhitePointLms;
         Vector3 targetColorLms = Vector3.Multiply(vector, sourceColorLms);
 
-        Matrix4x4.Invert(matrix, out Matrix4x4 inverseMatrix);
         return new CieXyz(Vector3.Transform(targetColorLms, inverseMatrix));
     }
 
     /// <summary>
-    /// Performs a bulk linear transformation of a source color in to the destination color.
+    /// Performs a bulk linear transformation of a source color in to the destination color using a
+    /// precomputed inverse of <paramref name="matrix"/>.
     /// </summary>
-    /// <remarks>Doesn't crop the resulting color space coordinates (e. g. allows negative values for XYZ coordinates).</remarks>
+    /// <remarks>
+    /// For callers that already hold the inverse, e.g. <see cref="ColorConversionOptions.InverseAdaptationMatrix"/>,
+    /// to avoid repeating <see cref="Matrix4x4.Invert"/> on every call.
+    /// </remarks>
     /// <param name="source">The span to the source colors.</param>
     /// <param name="destination">The span to the destination colors.</param>
     /// <param name="whitePoints">The conversion white points.</param>
     /// <param name="matrix">The chromatic adaptation matrix.</param>
-    public static void Transform(
+    /// <param name="inverseMatrix">The inverse of <paramref name="matrix"/>.</param>
+    internal static void Transform(
         ReadOnlySpan<CieXyz> source,
         Span<CieXyz> destination,
         (CieXyz From, CieXyz To) whitePoints,
-        Matrix4x4 matrix)
+        Matrix4x4 matrix,
+        Matrix4x4 inverseMatrix)
     {
         Guard.DestinationShouldNotBeTooShort(source, destination, nameof(destination));
         int count = source.Length;
@@ -71,8 +117,6 @@ public static class VonKriesChromaticAdaptation
             return;
         }
 
-        Matrix4x4.Invert(matrix, out Matrix4x4 inverseMatrix);
-
         ref CieXyz sourceBase = ref MemoryMarshal.GetReference(source);
         ref CieXyz destinationBase = ref MemoryMarshal.GetReference(destination);
 

src/ImageSharp/ColorProfiles/WorkingSpaces/RgbWorkingSpace.cs

@@ -19,6 +19,12 @@ public abstract class RgbWorkingSpace
     {
         this.WhitePoint = referenceWhite;
         this.ChromaticityCoordinates = chromaticityCoordinates;
+
+        Matrix4x4 rgbToCieXyz = CreateRgbToCieXyzMatrix(referenceWhite, chromaticityCoordinates);
+        this.RgbToCieXyzMatrix = rgbToCieXyz;
+
+        _ = Matrix4x4.Invert(rgbToCieXyz, out Matrix4x4 cieXyzToRgb);
+        this.CieXyzToRgbMatrix = cieXyzToRgb;
     }
 
     /// <summary>
@@ -31,6 +37,17 @@ public abstract class RgbWorkingSpace
     /// </summary>
     public RgbPrimariesChromaticityCoordinates ChromaticityCoordinates { get; }
 
+    /// <summary>
+    /// Gets the matrix transforming linear rgb coordinates in this working space to CIE XYZ.
+    /// </summary>
+    internal Matrix4x4 RgbToCieXyzMatrix { get; }
+
+    /// <summary>
+    /// Gets the inverse of <see cref="RgbToCieXyzMatrix"/>, transforming CIE XYZ to linear rgb
+    /// coordinates in this working space.
+    /// </summary>
+    internal Matrix4x4 CieXyzToRgbMatrix { get; }
+
     /// <summary>
     /// Compresses the linear vectors to their nonlinear equivalents with respect to the energy.
     /// </summary>
@@ -84,4 +101,56 @@ public abstract class RgbWorkingSpace
     /// <inheritdoc/>
     public override int GetHashCode()
         => HashCode.Combine(this.GetType(), this.WhitePoint, this.ChromaticityCoordinates);
+
+    private static Matrix4x4 CreateRgbToCieXyzMatrix(CieXyz referenceWhite, RgbPrimariesChromaticityCoordinates chromaticityCoordinates)
+    {
+        float xr = chromaticityCoordinates.R.X;
+        float xg = chromaticityCoordinates.G.X;
+        float xb = chromaticityCoordinates.B.X;
+        float yr = chromaticityCoordinates.R.Y;
+        float yg = chromaticityCoordinates.G.Y;
+        float yb = chromaticityCoordinates.B.Y;
+
+        float mXr = xr / yr;
+        float mZr = (1 - xr - yr) / yr;
+
+        float mXg = xg / yg;
+        float mZg = (1 - xg - yg) / yg;
+
+        float mXb = xb / yb;
+        float mZb = (1 - xb - yb) / yb;
+
+        Matrix4x4 xyzMatrix = new()
+        {
+            M11 = mXr,
+            M21 = mXg,
+            M31 = mXb,
+            M12 = 1F,
+            M22 = 1F,
+            M32 = 1F,
+            M13 = mZr,
+            M23 = mZg,
+            M33 = mZb,
+            M44 = 1F
+        };
+
+        Matrix4x4.Invert(xyzMatrix, out Matrix4x4 inverseXyzMatrix);
+
+        Vector3 vector = Vector3.Transform(referenceWhite.AsVector3Unsafe(), inverseXyzMatrix);
+
+        // Use transposed Rows/Columns
+        return new Matrix4x4
+        {
+            M11 = vector.X * mXr,
+            M21 = vector.Y * mXg,
+            M31 = vector.Z * mXb,
+            M12 = vector.X,
+            M22 = vector.Y,
+            M32 = vector.Z,
+            M13 = vector.X * mZr,
+            M23 = vector.Y * mZg,
+            M33 = vector.Z * mZb,
+            M44 = 1F
+        };
+    }
 }

src/ImageSharp/Metadata/Profiles/ICC/IccProfile.SRGB.cs

@@ -26,7 +26,7 @@ public sealed partial class IccProfile
     /// 3) Require rTRC, gTRC, bTRC to exist and be identical by parameters or sampled shape.
     /// 4) Accept if rXYZ/gXYZ/bXYZ already match the D50-adapted sRGB colorants within tolerance.
     /// 5) If white point ≈ D65, adapt only the colorant columns to D50 using Bradford
-    ///    via <see cref="VonKriesChromaticAdaptation.Transform(in CieXyz, ValueTuple{CieXyz, CieXyz}, Matrix4x4)"/> and then compare.
+    ///    via <see cref="VonKriesChromaticAdaptation.Transform(in CieXyz, ValueTuple{CieXyz, CieXyz}, Matrix4x4, Matrix4x4)"/> and then compare.
     /// This rejects channel-swapped and appearance profiles while allowing real sRGB.
     /// </summary>
     /// <remarks>
@@ -139,10 +139,11 @@ public sealed partial class IccProfile
             CieXyz fromWp = new(wtpt);          // Declared white
             CieXyz toWp = KnownIlluminants.D50; // PCS white
             Matrix4x4 matrix = KnownChromaticAdaptationMatrices.Bradford;
+            Matrix4x4.Invert(matrix, out Matrix4x4 inverseMatrix);
 
-            rXYZ = VonKriesChromaticAdaptation.Transform(new CieXyz(rXYZ), (fromWp, toWp), matrix).AsVector3Unsafe();
+            rXYZ = VonKriesChromaticAdaptation.Transform(new CieXyz(rXYZ), (fromWp, toWp), matrix, inverseMatrix).AsVector3Unsafe();
-            gXYZ = VonKriesChromaticAdaptation.Transform(new CieXyz(gXYZ), (fromWp, toWp), matrix).AsVector3Unsafe();
+            gXYZ = VonKriesChromaticAdaptation.Transform(new CieXyz(gXYZ), (fromWp, toWp), matrix, inverseMatrix).AsVector3Unsafe();
-            bXYZ = VonKriesChromaticAdaptation.Transform(new CieXyz(bXYZ), (fromWp, toWp), matrix).AsVector3Unsafe();
+            bXYZ = VonKriesChromaticAdaptation.Transform(new CieXyz(bXYZ), (fromWp, toWp), matrix, inverseMatrix).AsVector3Unsafe();
         }
 
         // Require identity mapping of primaries, no permutation