Support loading sprites with pre-multiplied alpha.

OpenRA.Game/Graphics/SheetBuilder.cs

@@ -82,16 +82,16 @@ namespace OpenRA.Graphics
 			this.margin = margin;
 		}
 
-		public Sprite Add(ISpriteFrame frame) { return Add(frame.Data, frame.Type, frame.Size, 0, frame.Offset); }
+		public Sprite Add(ISpriteFrame frame, bool premultiplied = false) { return Add(frame.Data, frame.Type, frame.Size, 0, frame.Offset, premultiplied); }
-		public Sprite Add(byte[] src, SpriteFrameType type, Size size) { return Add(src, type, size, 0, float3.Zero); }
+		public Sprite Add(byte[] src, SpriteFrameType type, Size size, bool premultiplied = false) { return Add(src, type, size, 0, float3.Zero, premultiplied); }
-		public Sprite Add(byte[] src, SpriteFrameType type, Size size, float zRamp, in float3 spriteOffset)
+		public Sprite Add(byte[] src, SpriteFrameType type, Size size, float zRamp, in float3 spriteOffset, bool premultiplied = false)
 		{
 			// Don't bother allocating empty sprites
 			if (size.Width == 0 || size.Height == 0)
 				return new Sprite(Current, Rectangle.Empty, 0, spriteOffset, CurrentChannel, BlendMode.Alpha);
 
 			var rect = Allocate(size, zRamp, spriteOffset);
-			Util.FastCopyIntoChannel(rect, src, type);
+			Util.FastCopyIntoChannel(rect, src, type, premultiplied);
 			Current.CommitBufferedData();
 			return rect;
 		}

OpenRA.Game/Graphics/SpriteCache.cs

@@ -24,7 +24,7 @@ namespace OpenRA.Graphics
 		readonly ISpriteLoader[] loaders;
 		readonly IReadOnlyFileSystem fileSystem;
 
-		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location)> spriteReservations = new();
+		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location, bool Premultiplied)> spriteReservations = new();
 		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location)> frameReservations = new();
 		readonly Dictionary<string, List<int>> reservationsByFilename = new();
 
@@ -47,10 +47,10 @@ namespace OpenRA.Graphics
 			this.loaders = loaders;
 		}
 
-		public int ReserveSprites(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location)
+		public int ReserveSprites(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location, bool premultiplied = false)
 		{
 			var token = nextReservationToken++;
-			spriteReservations[token] = (frames?.ToArray(), location);
+			spriteReservations[token] = (frames?.ToArray(), location, premultiplied);
 			reservationsByFilename.GetOrAdd(filename, _ => new List<int>()).Add(token);
 			return token;
 		}
@@ -91,14 +91,14 @@ namespace OpenRA.Graphics
 				var loadedFrames = GetFrames(fileSystem, filename, loaders, out _);
 				foreach (var token in tokens)
 				{
-					if (frameReservations.TryGetValue(token, out var r))
+					if (frameReservations.TryGetValue(token, out var rf))
 					{
 						if (loadedFrames != null)
 						{
-							if (r.Frames != null)
+							if (rf.Frames != null)
 							{
 								var resolved = new ISpriteFrame[loadedFrames.Length];
-								foreach (var i in r.Frames)
+								foreach (var i in rf.Frames)
 									resolved[i] = loadedFrames[i];
 								resolvedFrames[token] = resolved;
 							}
@@ -108,26 +108,32 @@ namespace OpenRA.Graphics
 						else
 						{
 							resolvedFrames[token] = null;
-							missingFiles[token] = (filename, r.Location);
+							missingFiles[token] = (filename, rf.Location);
 						}
 					}
 
-					if (spriteReservations.TryGetValue(token, out r))
+					if (spriteReservations.TryGetValue(token, out var rs))
 					{
 						if (loadedFrames != null)
 						{
 							var resolved = new Sprite[loadedFrames.Length];
-							var frames = r.Frames ?? Enumerable.Range(0, loadedFrames.Length);
+							var frames = rs.Frames ?? Enumerable.Range(0, loadedFrames.Length);
+
+							// Premultiplied and non-premultiplied sprites must be cached separately
+							// to cover the case where the same image is requested in both versions.
+							// The premultiplied sprites are stored with an index offset for efficiency
+							// rather than allocating a second dictionary.
+							var di = rs.Premultiplied ? loadedFrames.Length : 0;
 							foreach (var i in frames)
-								resolved[i] = spriteCache.GetOrAdd(i,
+								resolved[i] = spriteCache.GetOrAdd(i + di,
-									f => SheetBuilders[SheetBuilder.FrameTypeToSheetType(loadedFrames[f].Type)].Add(loadedFrames[f]));
+									f => SheetBuilders[SheetBuilder.FrameTypeToSheetType(loadedFrames[f - di].Type)].Add(loadedFrames[f - di], rs.Premultiplied));
 
 							resolvedSprites[token] = resolved;
 						}
 						else
 						{
 							resolvedSprites[token] = null;
-							missingFiles[token] = (filename, r.Location);
+							missingFiles[token] = (filename, rs.Location);
 						}
 					}
 				}

OpenRA.Game/Graphics/Util.cs

@@ -103,7 +103,7 @@ namespace OpenRA.Graphics
 			vertices[nv + 3] = new Vertex(d, r.Left, r.Bottom, sl, sb, uAttribC, tint, alpha);
 		}
 
-		public static void FastCopyIntoChannel(Sprite dest, byte[] src, SpriteFrameType srcType)
+		public static void FastCopyIntoChannel(Sprite dest, byte[] src, SpriteFrameType srcType, bool premultiplied = false)
 		{
 			var destData = dest.Sheet.GetData();
 			var width = dest.Bounds.Width;
@@ -154,6 +154,9 @@ namespace OpenRA.Graphics
 								}
 
 								var cc = Color.FromArgb(a, r, g, b);
+								if (premultiplied)
+									data[(y + j) * destStride + x + i] = cc.ToArgb();
+								else
 									data[(y + j) * destStride + x + i] = PremultiplyAlpha(cc).ToArgb();
 							}
 						}