Use EmbeddedSpritePalette in D2k.

OpenRA.Mods.D2k/Traits/World/D2kFogPalette.cs

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+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+using OpenRA.Graphics;
+using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.D2k.Traits
+{
+	class D2kFogPaletteInfo : ITraitInfo
+	{
+		[FieldLoader.Require, PaletteDefinition]
+		[Desc("Internal palette name")]
+		public readonly string Name = null;
+
+		[FieldLoader.Require, PaletteReference]
+		[Desc("The name of the shroud palette to base off.")]
+		public readonly string BasePalette = null;
+
+		[Desc("Allow palette modifiers to change the palette.")]
+		public readonly bool AllowModifiers = true;
+
+		public object Create(ActorInitializer init) { return new D2kFogPalette(this); }
+	}
+
+	class D2kFogPalette : ILoadsPalettes, IProvidesAssetBrowserPalettes
+	{
+		readonly D2kFogPaletteInfo info;
+		public D2kFogPalette(D2kFogPaletteInfo info) { this.info = info; }
+
+		public void LoadPalettes(WorldRenderer wr)
+		{
+			var basePalette = wr.Palette(info.BasePalette).Palette;
+
+			// Bit twiddling is equivalent to unpacking RGB channels, dividing them by 2, subtracting from 255, then repacking
+			var fog = new uint[Palette.Size];
+			for (var i = 0; i < Palette.Size; i++)
+				fog[i] = ~((basePalette[i] >> 1) & 0x007F7F7F);
+
+			wr.AddPalette(info.Name, new ImmutablePalette(fog), info.AllowModifiers);
+		}
+
+		public IEnumerable<string> PaletteNames { get { yield return info.Name; } }
+	}
+}