C# WinAPIを使ったHLS色構造体

動作確認環境：C# 9.0（.NET 5）

WinAPIを使ったHLS色構造体のコードです。Color型およびタプル（Tuple<ushort, ushort, ushort>およびValueTuple<ushort, ushort, ushort>）との相互変換をサポートしています。Colorとは異なりひとつの整数で表すことを前程としないため、IComparableおよびIComparable<T>は実装しません。同様の理由からColorとの明示的なキャストをサポートしません。

C# 9.0機能の練習も兼ねています。

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;

var hls = new HLSColor(0, 100, 20);
var rgb = hls.ToColor();
hls += new HLSColor(2, 2, 2);

public struct HLSColor : IEquatable<HLSColor>, ISerializable
{
    public ushort H;
    public ushort L;
    public ushort S;

    #region コンストラクタ
    public HLSColor(ushort h, ushort l, ushort s)
        => (H, L, S) = (h, l, s);
    public HLSColor(Tuple<ushort, ushort, ushort> value)
        => (H, L, S) = (value.Item1, value.Item2, value.Item3);
    public HLSColor(in ValueTuple<ushort, ushort, ushort> value)
        => (H, L, S) = (value.Item1, value.Item2, value.Item3);
    public HLSColor(SerializationInfo info, StreamingContext context)
        => (H, L, S) = (info.GetUInt16("H"), info.GetUInt16("L"), info.GetUInt16("S"));
    #endregion

    #region 一般の比較・文字列化関数
    public bool Equals(HLSColor other)
        => H == other.H && L == other.L && S == other.S;
    public override bool Equals(object obj)
        => obj is HLSColor hls2 && Equals(hls2);
    public override int GetHashCode()
        => ToValueTuple().GetHashCode();
    public override string ToString()
        => string.Format("HLS=({0},{1},{2})", H, L, S);
    #endregion

    #region Colorとの相互変換関数
    public static HLSColor FromColor(Color color)
    {
        NativeMethods.ColorRGBToHLS(unchecked((uint)color.ToArgb()), out var h, out var l, out var s);
        return new HLSColor(h, l, s);
    }
    public Color ToColor()
        => Color.FromArgb(unchecked((int)NativeMethods.ColorHLSToRGB(H, L, S)));
    #endregion

    #region シリアル化
    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (info == null)
            throw new ArgumentNullException(nameof(info));
        info.AddValue("H", H);
        info.AddValue("L", L);
        info.AddValue("S", S);
    }
    #endregion

    #region 比較演算子
    public static bool operator ==(HLSColor v1, HLSColor v2)
        => v1.Equals(v2);
    public static bool operator !=(HLSColor v1, HLSColor v2)
        => !v1.Equals(v2);
    /// <summary>加算。和がushortの最大値超過の場合は0xffffに抑えます。</summary>
    public static HLSColor operator +(HLSColor v1, HLSColor v2)
        => new HLSColor(ClampAddUInt16(v1.H, v2.H), ClampAddUInt16(v1.L, v2.L), ClampAddUInt16(v1.S, v2.S));
    /// <summary>減算。差がushortの最小値未満の場合は0に抑えます。</summary>
    public static HLSColor operator -(HLSColor v1, HLSColor v2)
        => new HLSColor(ClampDiffUInt16(v1.H, v2.H), ClampDiffUInt16(v1.L, v2.L), ClampDiffUInt16(v1.S, v2.S));
    #endregion

    #region タプルとの相互変換
    public ValueTuple<ushort, ushort, ushort> ToValueTuple()
        => ValueTuple.Create(H, S, L);
    public Tuple<ushort, ushort, ushort> ToTuple()
        => Tuple.Create(H, S, L);
    public static explicit operator Tuple<ushort, ushort, ushort>(HLSColor value)
        => value.ToTuple();
    public static explicit operator ValueTuple<ushort, ushort, ushort>(HLSColor value)
        => value.ToValueTuple();
    public static explicit operator HLSColor(Tuple<ushort, ushort, ushort> value)
        => new HLSColor(value);
    public static explicit operator HLSColor(ValueTuple<ushort, ushort, ushort> value)
        => new HLSColor(value);
    #endregion

    #region 補助関数
    private static ushort ClampAddUInt16(ushort x, ushort y)
        => (x + y) switch { int z when z > 0xffffu => (ushort)0xffffu, int z => (ushort)z };
    private static ushort ClampDiffUInt16(ushort x, ushort y)
        => (x - y) switch { int z when z > 0 => (ushort)z, _ => 0 };
    #endregion

    private static class NativeMethods
    {
        [DllImport("shlwapi.dll")]
        public static extern uint ColorHLSToRGB(ushort wHue, ushort wLuminance, ushort wSaturation);
        [DllImport("shlwapi.dll")]
        public static extern void ColorRGBToHLS(uint clrRGB, out ushort pwHue, out ushort pwLuminance, out ushort pwSaturation);
    }
}