diff --git a/src/ImageSharp/ColorProfiles/HunterLab.cs b/src/ImageSharp/ColorProfiles/HunterLab.cs new file mode 100644 index 0000000000..cf6dbd363b --- /dev/null +++ b/src/ImageSharp/ColorProfiles/HunterLab.cs @@ -0,0 +1,202 @@ +// Copyright (c) Six Labors. +// Licensed under the Six Labors Split License. + +using System.Numerics; +using System.Runtime.CompilerServices; + +namespace SixLabors.ImageSharp.ColorProfiles; + +/// +/// Represents an Hunter LAB color. +/// . +/// +public readonly struct HunterLab : IColorProfile +{ + /// + /// Initializes a new instance of the struct. + /// + /// The lightness dimension. + /// The a (green - magenta) component. + /// The b (blue - yellow) component. + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public HunterLab(float l, float a, float b) + : this(new Vector3(l, a, b)) + { + } + + /// + /// Initializes a new instance of the struct. + /// + /// The vector representing the l a b components. + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public HunterLab(Vector3 vector) + { + // Not clamping as documentation about this space only indicates "usual" ranges + this.L = vector.X; + this.A = vector.Y; + this.B = vector.Z; + } + + /// + /// Gets the lightness dimension. + /// A value usually ranging between 0 (black), 100 (diffuse white) or higher (specular white). + /// + public readonly float L { get; } + + /// + /// Gets the a color component. + /// A value usually ranging from -100 to 100. Negative is green, positive magenta. + /// + public readonly float A { get; } + + /// + /// Gets the b color component. + /// A value usually ranging from -100 to 100. Negative is blue, positive is yellow + /// + public readonly float B { get; } + + /// + /// Gets the reference white point of this color. + /// + public readonly CieXyz WhitePoint { get; } + + /// + /// Compares two objects for equality. + /// + /// The on the left side of the operand. + /// The on the right side of the operand. + /// + /// True if the current left is equal to the parameter; otherwise, false. + /// + public static bool operator ==(HunterLab left, HunterLab right) => left.Equals(right); + + /// + /// Compares two objects for inequality + /// + /// The on the left side of the operand. + /// The on the right side of the operand. + /// + /// True if the current left is unequal to the parameter; otherwise, false. + /// + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public static bool operator !=(HunterLab left, HunterLab right) => !left.Equals(right); + + /// + public static HunterLab FromProfileConnectingSpace(ColorConversionOptions options, in CieXyz source) + { + // Conversion algorithm described here: + // http://en.wikipedia.org/wiki/Lab_color_space#Hunter_Lab + CieXyz whitePoint = options.TargetWhitePoint; + float x = source.X, y = source.Y, z = source.Z; + float xn = whitePoint.X, yn = whitePoint.Y, zn = whitePoint.Z; + + float ka = ComputeKa(in whitePoint); + float kb = ComputeKb(in whitePoint); + + float yByYn = y / yn; + float sqrtYbyYn = MathF.Sqrt(yByYn); + float l = 100 * sqrtYbyYn; + float a = ka * (((x / xn) - yByYn) / sqrtYbyYn); + float b = kb * ((yByYn - (z / zn)) / sqrtYbyYn); + + if (float.IsNaN(a)) + { + a = 0; + } + + if (float.IsNaN(b)) + { + b = 0; + } + + return new HunterLab(l, a, b); + } + + /// + public static void FromProfileConnectionSpace(ColorConversionOptions options, ReadOnlySpan source, Span destination) + { + Guard.DestinationShouldNotBeTooShort(source, destination, nameof(destination)); + for (int i = 0; i < source.Length; i++) + { + CieXyz xyz = source[i]; + destination[i] = FromProfileConnectingSpace(options, in xyz); + } + } + + /// + public CieXyz ToProfileConnectingSpace(ColorConversionOptions options) + { + // Conversion algorithm described here: + // http://en.wikipedia.org/wiki/Lab_color_space#Hunter_Lab + CieXyz whitePoint = options.WhitePoint; + float l = this.L, a = this.A, b = this.B; + float xn = whitePoint.X, yn = whitePoint.Y, zn = whitePoint.Z; + + float ka = ComputeKa(whitePoint); + float kb = ComputeKb(whitePoint); + + float pow = Numerics.Pow2(l / 100F); + float sqrtPow = MathF.Sqrt(pow); + float y = pow * yn; + + float x = (((a / ka) * sqrtPow) + pow) * xn; + float z = (((b / kb) * sqrtPow) - pow) * (-zn); + + return new CieXyz(x, y, z); + } + + /// + public static void ToProfileConnectionSpace(ColorConversionOptions options, ReadOnlySpan source, Span destination) + { + Guard.DestinationShouldNotBeTooShort(source, destination, nameof(destination)); + for (int i = 0; i < source.Length; i++) + { + HunterLab lab = source[i]; + destination[i] = lab.ToProfileConnectingSpace(options); + } + } + + /// + public static ChromaticAdaptionWhitePointSource GetChromaticAdaptionWhitePointSource() + => ChromaticAdaptionWhitePointSource.WhitePoint; + + /// + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public override int GetHashCode() => HashCode.Combine(this.L, this.A, this.B, this.WhitePoint); + + /// + public override string ToString() => FormattableString.Invariant($"HunterLab({this.L:#0.##}, {this.A:#0.##}, {this.B:#0.##})"); + + /// + public override bool Equals(object? obj) => obj is HunterLab other && this.Equals(other); + + /// + [MethodImpl(MethodImplOptions.AggressiveInlining)] + public bool Equals(HunterLab other) + => this.L.Equals(other.L) + && this.A.Equals(other.A) + && this.B.Equals(other.B) + && this.WhitePoint.Equals(other.WhitePoint); + + [MethodImpl(MethodImplOptions.AggressiveInlining)] + private static float ComputeKa(in CieXyz whitePoint) + { + if (whitePoint.Equals(Illuminants.C)) + { + return 175F; + } + + return 100F * (175F / 198.04F) * (whitePoint.X + whitePoint.Y); + } + + [MethodImpl(MethodImplOptions.AggressiveInlining)] + private static float ComputeKb(in CieXyz whitePoint) + { + if (whitePoint == Illuminants.C) + { + return 70F; + } + + return 100F * (70F / 218.11F) * (whitePoint.Y + whitePoint.Z); + } +}