LmsAdaptationMatrix.cs

// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.

using System.Numerics;

namespace SixLabors.ImageSharp.ColorSpaces.Conversion
{
    /// <summary>
    /// Matrices used for transformation from <see cref="CieXyz"/> to <see cref="Lms"/>, defining the cone response domain.
    /// Used in <see cref="IChromaticAdaptation"/>
    /// </summary>
    /// <remarks>
    /// Matrix data obtained from:
    /// Two New von Kries Based Chromatic Adaptation Transforms Found by Numerical Optimization
    /// S. Bianco, R. Schettini
    /// DISCo, Department of Informatics, Systems and Communication, University of Milan-Bicocca, viale Sarca 336, 20126 Milan, Italy
    /// https://web.stanford.edu/~sujason/ColorBalancing/Papers/Two%20New%20von%20Kries%20Based%20Chromatic%20Adaptation.pdf
    /// </remarks>
    public static class LmsAdaptationMatrix
    {
        /// <summary>
        /// Von Kries chromatic adaptation transform matrix (Hunt-Pointer-Estevez adjusted for D65)
        /// </summary>
        public static readonly Matrix4x4 VonKriesHPEAdjusted
            = Matrix4x4.Transpose(new Matrix4x4
            {
                M11 = 0.40024F,
                M12 = 0.7076F,
                M13 = -0.08081F,
                M21 = -0.2263F,
                M22 = 1.16532F,
                M23 = 0.0457F,
                M31 = 0,
                M32 = 0,
                M33 = 0.91822F,
                M44 = 1F // Important for inverse transforms.
            });

        /// <summary>
        /// Von Kries chromatic adaptation transform matrix (Hunt-Pointer-Estevez for equal energy)
        /// </summary>
        public static readonly Matrix4x4 VonKriesHPE
            = Matrix4x4.Transpose(new Matrix4x4
            {
                M11 = 0.3897F,
                M12 = 0.6890F,
                M13 = -0.0787F,
                M21 = -0.2298F,
                M22 = 1.1834F,
                M23 = 0.0464F,
                M31 = 0,
                M32 = 0,
                M33 = 1F,
                M44 = 1F
            });

        /// <summary>
        /// XYZ scaling chromatic adaptation transform matrix
        /// </summary>
        public static readonly Matrix4x4 XyzScaling = Matrix4x4.Transpose(Matrix4x4.Identity);

        /// <summary>
        /// Bradford chromatic adaptation transform matrix (used in CMCCAT97)
        /// </summary>
        public static readonly Matrix4x4 Bradford
            = Matrix4x4.Transpose(new Matrix4x4
            {
                M11 = 0.8951F,
                M12 = 0.2664F,
                M13 = -0.1614F,
                M21 = -0.7502F,
                M22 = 1.7135F,
                M23 = 0.0367F,
                M31 = 0.0389F,
                M32 = -0.0685F,
                M33 = 1.0296F,
                M44 = 1F
            });

        /// <summary>
        /// Spectral sharpening and the Bradford transform
        /// </summary>
        public static readonly Matrix4x4 BradfordSharp
            = Matrix4x4.Transpose(new Matrix4x4
            {
                M11 = 1.2694F,
                M12 = -0.0988F,
                M13 = -0.1706F,
                M21 = -0.8364F,
                M22 = 1.8006F,
                M23 = 0.0357F,
                M31 = 0.0297F,
                M32 = -0.0315F,
                M33 = 1.0018F,
                M44 = 1F
            });

        /// <summary>
        /// CMCCAT2000 (fitted from all available color data sets)
        /// </summary>
        public static readonly Matrix4x4 CMCCAT2000
            = Matrix4x4.Transpose(new Matrix4x4
            {
                M11 = 0.7982F,
                M12 = 0.3389F,
                M13 = -0.1371F,
                M21 = -0.5918F,
                M22 = 1.5512F,
                M23 = 0.0406F,
                M31 = 0.0008F,
                M32 = 0.239F,
                M33 = 0.9753F,
                M44 = 1F
            });

        /// <summary>
        /// CAT02 (optimized for minimizing CIELAB differences)
        /// </summary>
        public static readonly Matrix4x4 CAT02
            = Matrix4x4.Transpose(new Matrix4x4
            {
                M11 = 0.7328F,
                M12 = 0.4296F,
                M13 = -0.1624F,
                M21 = -0.7036F,
                M22 = 1.6975F,
                M23 = 0.0061F,
                M31 = 0.0030F,
                M32 = 0.0136F,
                M33 = 0.9834F,
                M44 = 1F
            });
    }
}