Preserve original brightness when remapping player colors.

OpenRA.Game/Graphics/PlayerColorRemap.cs

@@ -18,43 +18,34 @@ namespace OpenRA.Graphics
 {
 	public class PlayerColorRemap : IPaletteRemap
 	{
-		Dictionary<int, Color> remapColors;
+		readonly int[] remapIndices;
+		readonly float hue;
+		readonly float saturation;
 
-		public static int GetRemapIndex(int[] ramp, int i)
+		public PlayerColorRemap(int[] remapIndices, float hue, float saturation)
 		{
-			return ramp[i];
-		}
-
-		public PlayerColorRemap(int[] ramp, Color c, float rampFraction)
-		{
-			var h = c.GetHue() / 360.0f;
-			var s = c.GetSaturation();
-			var l = c.GetBrightness();
-
-			// Increase luminosity if required to represent the full ramp
-			var rampRange = (byte)((1 - rampFraction) * l);
-			var c1 = Color.FromAhsl(h, s, Math.Max(rampRange, l));
-			var c2 = Color.FromAhsl(h, s, (byte)Math.Max(0, l - rampRange));
-			var baseIndex = ramp[0];
-			var remapRamp = ramp.Select(r => r - ramp[0]);
-			var rampMaxIndex = ramp.Length - 1;
-
-			// reversed remapping
-			if (ramp[0] > ramp[rampMaxIndex])
-			{
-				baseIndex = ramp[rampMaxIndex];
-				for (var i = rampMaxIndex; i > 0; i--)
-					remapRamp = ramp.Select(r => r - ramp[rampMaxIndex]);
-			}
-
-			remapColors = remapRamp.Select((x, i) => (baseIndex + i, Exts.ColorLerp(x / (float)ramp.Length, c1, c2)))
-				.ToDictionary(u => u.Item1, u => u.Item2);
+			this.remapIndices = remapIndices;
+			this.hue = hue;
+			this.saturation = saturation;
 		}
 
 		public Color GetRemappedColor(Color original, int index)
 		{
-			return remapColors.TryGetValue(index, out var c)
-				? c : original;
+			if (!remapIndices.Contains(index))
+				return original;
+
+			// Color remapping is applied in a linear color space, so start
+			// by undoing the pre-multiplied alpha and gamma corrections
+			var (r, g, b) = original.ToLinear();
+
+			// Calculate the brightness (i.e HSV value) of the original colour
+			var value = Math.Max(Math.Max(r, g), b);
+
+			// Construct the new RGB color
+			(r, g, b) = Color.HsvToRgb(hue, saturation, value);
+
+			// Convert linear back to SRGB and pre-multiply by the alpha
+			return Color.FromLinear(original.A, r, g, b);
 		}
 	}
 }

OpenRA.Game/Traits/Player/PlayerColorPalette.cs

@@ -29,9 +29,6 @@ namespace OpenRA.Traits
 		[Desc("Remap these indices to player colors.")]
 		public readonly int[] RemapIndex = { };
 
-		[Desc("Luminosity range to span.")]
-		public readonly float Ramp = 0.05f;
-
 		[Desc("Allow palette modifiers to change the palette.")]
 		public readonly bool AllowModifiers = true;
 
@@ -49,7 +46,9 @@ namespace OpenRA.Traits
 
 		public void LoadPlayerPalettes(WorldRenderer wr, string playerName, Color color, bool replaceExisting)
 		{
-			var remap = new PlayerColorRemap(info.RemapIndex, color, info.Ramp);
+			color.ToAhsv(out _, out var h, out var s, out _);
+
+			var remap = new PlayerColorRemap(info.RemapIndex, h, s);
 			var pal = new ImmutablePalette(wr.Palette(info.BasePalette).Palette, remap);
 			wr.AddPalette(info.BaseName + playerName, pal, info.AllowModifiers, replaceExisting);
 		}

OpenRA.Game/Traits/World/FixedColorPalette.cs

@@ -31,9 +31,6 @@ namespace OpenRA.Traits
 		[Desc("The fixed color to remap.")]
 		public readonly Color Color;
 
-		[Desc("Luminosity range to span.")]
-		public readonly float Ramp = 0.05f;
-
 		[Desc("Allow palette modifiers to change the palette.")]
 		public readonly bool AllowModifiers = true;
 
@@ -51,7 +48,9 @@ namespace OpenRA.Traits
 
 		public void LoadPalettes(WorldRenderer wr)
 		{
-			var remap = new PlayerColorRemap(info.RemapIndex, info.Color, info.Ramp);
+			info.Color.ToAhsv(out _, out var h, out var s, out _);
+
+			var remap = new PlayerColorRemap(info.RemapIndex, h, s);
 			wr.AddPalette(info.Name, new ImmutablePalette(wr.Palette(info.Base).Palette, remap), info.AllowModifiers);
 		}
 	}

OpenRA.Mods.Cnc/UtilityCommands/RemapShpCommand.cs

@@ -54,8 +54,7 @@ namespace OpenRA.Mods.Cnc.UtilityCommands
 
 			// the remap range is always 16 entries, but their location and order changes
 			for (var i = 0; i < 16; i++)
-				remap[PlayerColorRemap.GetRemapIndex(srcRemapIndex, i)]
-					= PlayerColorRemap.GetRemapIndex(destRemapIndex, i);
+				remap[srcRemapIndex[i]] = destRemapIndex[i];
 
 			// map everything else to the best match based on channel-wise distance
 			var srcPalette = new ImmutablePalette(args[1].Split(':')[1], new[] { 0 }, shadowIndex);

OpenRA.Mods.Common/Traits/World/ColorPickerManager.cs

@@ -40,16 +40,19 @@ namespace OpenRA.Mods.Common.Traits
 			"A dictionary of [faction name]: [actor name].")]
 		public readonly Dictionary<string, string> FactionPreviewActors = new Dictionary<string, string>();
 
+		[Desc("Remap these indices to player colors.")]
 		public readonly int[] RemapIndices = { };
-		public readonly float Ramp = 0.05f;
+
 		public Color Color { get; private set; }
 
 		public void Update(WorldRenderer worldRenderer, Color color)
 		{
 			Color = color;
 
+			Color.ToAhsv(out _, out var h, out var s, out _);
+
 			var newPalette = new MutablePalette(worldRenderer.Palette(PaletteName).Palette);
-			newPalette.ApplyRemap(new PlayerColorRemap(RemapIndices, Color, Ramp));
+			newPalette.ApplyRemap(new PlayerColorRemap(RemapIndices, h, s));
 			worldRenderer.ReplacePalette(PaletteName, newPalette);
 		}