Added Mask to Apply filter node

src/PixiEditor.ChangeableDocument/Changeables/Graph/Nodes/FilterNodes/ApplyFilterNode.cs

@@ -13,15 +13,24 @@ namespace PixiEditor.ChangeableDocument.Changeables.Graph.Nodes.FilterNodes;
 [NodeInfo("ApplyFilter")]
 public class ApplyFilterNode : RenderNode, IRenderInput
 {
-    private Paint _paint = new();
+    private readonly Paint _paint = new();
+    private readonly Paint _maskPaint = new()
+    {
+        BlendMode = BlendMode.DstIn,
+        ColorFilter = Filters.MaskFilter
+    };
+
     public InputProperty<Filter?> Filter { get; }
 
     public RenderInputProperty Background { get; }
 
+    public RenderInputProperty Mask { get; }
+
     public ApplyFilterNode()
     {
         Background = CreateRenderInput("Input", "IMAGE");
         Filter = CreateInput<Filter>("Filter", "FILTER", null);
+        Mask = CreateRenderInput("Mask", "MASK");
         Output.FirstInChain = null;
         AllowHighDpiRendering = true;
     }
@@ -33,45 +42,82 @@ public class ApplyFilterNode : RenderNode, IRenderInput
         base.Paint(context, surface);
     }
 
-    protected override void OnPaint(RenderContext context, DrawingSurface surface)
+    protected override void OnPaint(RenderContext context, DrawingSurface outputSurface)
     {
-        if (_paint == null)
-            return;
+        using var _ = DetermineTargetSurface(context, outputSurface, out var processingSurface);
+
+        DrawWithFilter(context, outputSurface, processingSurface);
+        
+        // If the Mask is null, we already drew to the output surface, otherwise we still need to draw to it (and apply the mask)
+        if (processingSurface != outputSurface)
+        {
+            ApplyWithMask(context, processingSurface, outputSurface);
+        }
+    }
 
+    private void DrawWithFilter(RenderContext context, DrawingSurface outputSurface, DrawingSurface processingSurface)
+    {
         _paint.SetFilters(Filter.Value);
 
         if (!context.ProcessingColorSpace.IsSrgb)
         {
-            var intermediate = Texture.ForProcessing(surface, context.ProcessingColorSpace);
+            HandleNonSrgbContext(context, outputSurface, processingSurface);
+            return;
+        }
+
+        var layer = processingSurface.Canvas.SaveLayer(_paint);
+        Background.Value?.Paint(context, processingSurface);
+        processingSurface.Canvas.RestoreToCount(layer);
+    }
 
-            int saved = surface.Canvas.Save();
-            surface.Canvas.SetMatrix(Matrix3X3.Identity);
+    private void HandleNonSrgbContext(RenderContext context, DrawingSurface surface, DrawingSurface targetSurface)
+    {
+        using var intermediate = Texture.ForProcessing(surface, context.ProcessingColorSpace);
 
-            Background.Value?.Paint(context, intermediate.DrawingSurface);
+        Background.Value?.Paint(context, intermediate.DrawingSurface);
 
-            var srgbSurface = Texture.ForProcessing(intermediate.Size, ColorSpace.CreateSrgb());
+        using var srgbSurface = Texture.ForProcessing(intermediate.Size, ColorSpace.CreateSrgb());
 
-            srgbSurface.DrawingSurface.Canvas.SaveLayer(_paint);
-            srgbSurface.DrawingSurface.Canvas.DrawSurface(intermediate.DrawingSurface, 0, 0);
-            srgbSurface.DrawingSurface.Canvas.Restore();
+        srgbSurface.DrawingSurface.Canvas.SaveLayer(_paint);
+        srgbSurface.DrawingSurface.Canvas.DrawSurface(intermediate.DrawingSurface, 0, 0);
+        srgbSurface.DrawingSurface.Canvas.Restore();
 
-            surface.Canvas.DrawSurface(srgbSurface.DrawingSurface, 0, 0);
-            surface.Canvas.RestoreToCount(saved);
-            intermediate.Dispose();
-            srgbSurface.Dispose();
-        }
-        else
-        {
-            int layer = surface.Canvas.SaveLayer(_paint);
-            Background.Value?.Paint(context, surface);
-            surface.Canvas.RestoreToCount(layer);
-        }
+        var saved = targetSurface.Canvas.Save();
+        targetSurface.Canvas.SetMatrix(Matrix3X3.Identity);
+
+        targetSurface.Canvas.DrawSurface(srgbSurface.DrawingSurface, 0, 0);
+        targetSurface.Canvas.RestoreToCount(saved);
     }
 
-    public override RectD? GetPreviewBounds(int frame, string elementToRenderName = "")
+    private Texture? DetermineTargetSurface(RenderContext context, DrawingSurface outputSurface, out DrawingSurface targetSurface)
     {
-        return PreviewUtils.FindPreviewBounds(Background.Connection, frame, elementToRenderName);
+        targetSurface = outputSurface;
+        
+        if (Mask.Value == null)
+            return null;
+        
+        Background.Value?.Paint(context, outputSurface);
+        var texture = Texture.ForProcessing(outputSurface, context.ProcessingColorSpace);
+        targetSurface = texture.DrawingSurface;
+        
+        return texture;
     }
 
+    private void ApplyWithMask(RenderContext context, DrawingSurface processedSurface, DrawingSurface finalSurface)
+    {
+        var maskLayer = processedSurface.Canvas.SaveLayer(_maskPaint);
+        Mask.Value?.Paint(context, processedSurface);
+        processedSurface.Canvas.RestoreToCount(maskLayer);
+
+        var saved = finalSurface.Canvas.Save();
+        finalSurface.Canvas.SetMatrix(Matrix3X3.Identity);
+
+        finalSurface.Canvas.DrawSurface(processedSurface, 0, 0);
+        finalSurface.Canvas.RestoreToCount(saved);
+    }
+
+    public override RectD? GetPreviewBounds(int frame, string elementToRenderName = "") =>
+        PreviewUtils.FindPreviewBounds(Background.Connection, frame, elementToRenderName);
+
     public override Node CreateCopy() => new ApplyFilterNode();
 }