Vanara/PInvoke/Shared/WinDef/COLORREF.cs

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

namespace Vanara.PInvoke
{
	/// <summary>The COLORREF value is used to specify an RGB color in the form <c>0x00bbggrr</c>.</summary>
	// typedef DWORD COLORREF;typedef DWORD* LPCOLORREF; https://msdn.microsoft.com/en-us/library/windows/desktop/dd183449(v=vs.85).aspx
	[PInvokeData("Windef.h", MSDNShortId = "dd183449")]
	[StructLayout(LayoutKind.Explicit, Size = 4)]
	public struct COLORREF
	{
		/// <summary>The DWORD value</summary>
		[FieldOffset(0)]
		private uint Value;

		/// <summary>The intensity of the red color.</summary>
		[FieldOffset(0)]
		public byte R;

		/// <summary>The intensity of the green color.</summary>
		[FieldOffset(1)]
		public byte G;

		/// <summary>The intensity of the blue color.</summary>
		[FieldOffset(2)]
		public byte B;

		/// <summary>The transparency.</summary>
		[FieldOffset(3)]
		public byte A;

		private const uint CLR_NONE = 0xFFFFFFFF;
		private const uint CLR_DEFAULT = 0xFF000000;

		/// <summary>Initializes a new instance of the <see cref="COLORREF"/> struct.</summary>
		/// <param name="r">The intensity of the red color.</param>
		/// <param name="g">The intensity of the green color.</param>
		/// <param name="b">The intensity of the blue color.</param>
		public COLORREF(byte r, byte g, byte b)
		{
			Value = 0;
			A = 0;
			R = r;
			G = g;
			B = b;
		}

		/// <summary>Initializes a new instance of the <see cref="COLORREF"/> struct.</summary>
		/// <param name="value">The packed DWORD value.</param>
		public COLORREF(uint value)
		{
			R = 0;
			G = 0;
			B = 0;
			A = 0;
			Value = value & 0x00FFFFFF;
		}

		/// <summary>Initializes a new instance of the <see cref="COLORREF"/> struct.</summary>
		/// <param name="color">The color.</param>
		public COLORREF(Color color) : this(color.R, color.G, color.B)
		{
			if (color == Color.Transparent)
				Value = CLR_NONE;
		}

		/// <summary>A method to darken a color by a percentage of the difference between the color and Black.</summary>
		/// <param name="percent">The percentage by which to darken the original color.</param>
		/// <returns>
		/// The return color's Alpha value will be unchanged, but the RGB content will have been increased by the specified percentage. If
		/// percent is 100 then the returned Color will be Black with original Alpha.
		/// </returns>
		public COLORREF Darken(float percent)
		{
			if (percent < 0 || percent > 1.0)
				throw new ArgumentOutOfRangeException(nameof(percent));

			return new(Conv(R), Conv(G), Conv(B)) { Value = Value };

			byte Conv(byte c) => (byte)(c - (int)(c * percent));
		}

		/// <summary>A method to lighten a color by a percentage of the difference between the color and Black.</summary>
		/// <param name="percent">The percentage by which to lighten the original color.</param>
		/// <returns>
		/// The return color's Alpha value will be unchanged, but the RGB content will have been decreased by the specified percentage. If
		/// percent is 100 then the returned Color will be White with original Alpha.
		/// </returns>
		public COLORREF Lighten(float percent)
		{
			if (percent < 0 || percent > 1.0)
				throw new ArgumentOutOfRangeException(nameof(percent));

			return new(Conv(R), Conv(G), Conv(B)) { Value = Value };

			byte Conv(byte c) => (byte)(c + (int)((255f - c) * percent));
		}

		/// <summary>Gets the 32-bit ARGB value of this <see cref="COLORREF"/> structure.</summary>
		/// <returns>The 32-bit ARGB value of this <see cref="COLORREF"/> structure.</returns>
		public int ToArgb() => unchecked((int)Value);

		/// <summary>Performs an implicit conversion from <see cref="COLORREF"/> to <see cref="Color"/>.</summary>
		/// <param name="cr">The <see cref="COLORREF"/> value.</param>
		/// <returns>The result of the conversion.</returns>
		public static implicit operator Color(COLORREF cr) => cr.Value == CLR_NONE ? Color.Transparent : Color.FromArgb(cr.R, cr.G, cr.B);

		/// <summary>Performs an implicit conversion from <see cref="Color"/> to <see cref="COLORREF"/>.</summary>
		/// <param name="clr">The <see cref="Color"/> value.</param>
		/// <returns>The result of the conversion.</returns>
		public static implicit operator COLORREF(Color clr) => new(clr);

		/// <summary>Performs an implicit conversion from <see cref="System.ValueTuple{R, G, B}"/> to <see cref="COLORREF"/>.</summary>
		/// <param name="clr">The tuple containing the R, G, and B values.</param>
		/// <returns>The resulting <see cref="COLORREF"/> instance from the conversion.</returns>
		public static implicit operator COLORREF((byte r, byte g, byte b) clr) => new(clr.r, clr.g, clr.b);

		/// <summary>Performs an implicit conversion from <see cref="COLORREF"/> to <see cref="System.UInt32"/>.</summary>
		/// <param name="cr">The <see cref="COLORREF"/> value.</param>
		/// <returns>The result of the conversion.</returns>
		public static implicit operator uint(COLORREF cr) => cr.Value;

		/// <summary>Performs an implicit conversion from <see cref="System.UInt32"/> to <see cref="COLORREF"/>.</summary>
		/// <param name="value">The <see cref="uint"/> value.</param>
		/// <returns>The result of the conversion.</returns>
		public static implicit operator COLORREF(uint value) => new(value);

		/// <summary>Static reference for CLR_NONE representing no color.</summary>
		public static COLORREF None = new(CLR_NONE);

		/// <summary>Static reference for CLR_DEFAULT representing the default color.</summary>
		public static COLORREF Default = new(0xFF000000);

		/// <inheritdoc />
		public override string ToString() => ((Color)this).ToString();
	}
}