feat(composition): Implement ExposureEffect + Sample

src/SamplesApp/UITests.Shared/Windows_UI_Composition/EffectBrushTests.xaml

@@ -21,5 +21,6 @@
 		<Grid x:Name="colorGrid" Width="200" Height="200" VerticalAlignment="Top" HorizontalAlignment="Left" ToolTipService.ToolTip="ColorSourceEffect"/>
 		<Grid x:Name="opacityGrid" Width="200" Height="200" VerticalAlignment="Top" HorizontalAlignment="Left" ToolTipService.ToolTip="OpacityEffect"/>
 		<Grid x:Name="contrastGrid" Width="200" Height="200" VerticalAlignment="Top" HorizontalAlignment="Left" ToolTipService.ToolTip="ContrastEffect"/>
+		<Grid x:Name="exposureGrid" Width="200" Height="200" VerticalAlignment="Top" HorizontalAlignment="Left" ToolTipService.ToolTip="ExposureEffect (Negative Value, -1)"/>
 	</GridView>
 </UserControl>

src/SamplesApp/UITests.Shared/Windows_UI_Composition/EffectBrushTests.xaml.cs

@@ -3,8 +3,6 @@
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
-using ShimSkiaSharp;
-using SkiaSharp;
 using Uno.Extensions;
 using Uno.UI.Samples.Controls;
 using Windows.Foundation;
@@ -88,7 +86,7 @@ private void EffectBrushTests_Loaded(object sender, RoutedEventArgs e)
 
 			blendGrid.Background = new EffectTesterBrushWithSecondaryBrush(effectBrush7, compositor.CreateColorBrush(Colors.LightBlue));
 
-			var surface = LoadedImageSurface.StartLoadFromUri(new Uri("https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Logo-winui.svg/200px-Logo-winui.svg.png"));
+			var surface = LoadedImageSurface.StartLoadFromUri(new Uri("https://user-images.githubusercontent.com/34550324/266135095-71c9ce0a-4e49-408f-b2ff-670a53adef10.png"));
 			surface.LoadCompleted += (s, o) =>
 			{
 				if (o.Status == LoadedImageSourceLoadStatus.Success)
@@ -120,6 +118,12 @@ private void EffectBrushTests_Loaded(object sender, RoutedEventArgs e)
 			var effectBrush11 = factory11.CreateBrush();
 
 			contrastGrid.Background = new EffectTesterBrush(effectBrush11);
+
+			var effect12 = new SimpleExposureEffect() { Source = new CompositionEffectSourceParameter("sourceBrush"), Exposure = -1.0f };
+			var factory12 = compositor.CreateEffectFactory(effect12);
+			var effectBrush12 = factory12.CreateBrush();
+
+			exposureGrid.Background = new EffectTesterBrush(effectBrush12);
 #endif
 		}
 
@@ -673,6 +677,60 @@ public object GetProperty(uint index)
 			public IGraphicsEffectSource GetSource(uint index) => Source;
 			public uint GetSourceCount() => 1;
 		}
+
+		[Guid("B56C8CFA-F634-41EE-BEE0-FFA617106004")]
+		private class SimpleExposureEffect : IGraphicsEffect, IGraphicsEffectSource, IGraphicsEffectD2D1Interop
+		{
+			private string _name = "SimpleExposureEffect";
+			private Guid _id = new Guid("B56C8CFA-F634-41EE-BEE0-FFA617106004");
+
+			public string Name
+			{
+				get => _name;
+				set => _name = value;
+			}
+
+			public float Exposure { get; set; } = 0.0f;
+
+			public IGraphicsEffectSource Source { get; set; }
+
+			public Guid GetEffectId() => _id;
+
+			public void GetNamedPropertyMapping(string name, out uint index, out GraphicsEffectPropertyMapping mapping)
+			{
+				switch (name)
+				{
+					case "Exposure":
+					case "ExposureValue":
+						{
+							index = 0;
+							mapping = GraphicsEffectPropertyMapping.Direct;
+							break;
+						}
+					default:
+						{
+							index = 0xFF;
+							mapping = (GraphicsEffectPropertyMapping)0xFF;
+							break;
+						}
+				}
+			}
+
+			public object GetProperty(uint index)
+			{
+				switch (index)
+				{
+					case 0:
+						return Exposure;
+					default:
+						return null;
+				}
+			}
+
+			public uint GetPropertyCount() => 1;
+			public IGraphicsEffectSource GetSource(uint index) => Source;
+			public uint GetSourceCount() => 1;
+		}
 #endif
 	}
 }

src/Uno.UI.Composition/Composition/CompositionEffectBrush.skia.cs

@@ -11,6 +11,7 @@ public partial class CompositionEffectBrush : CompositionBrush
 		private SKImageFilter GenerateEffectFilter(object effect, SKRect bounds)
 		{
 			// TODO: https://user-images.githubusercontent.com/34550324/264485558-d7ee5062-b0e0-4f6e-a8c7-0620ec561d3d.png
+			// TODO: Cache pixel shaders (see dwmcore.dll!CCompiledEffectCache)
 
 			switch (effect)
 			{
@@ -22,7 +23,7 @@ private SKImageFilter GenerateEffectFilter(object effect, SKRect bounds)
 							SKPaint paint = new SKPaint() { IsAntialias = true, IsAutohinted = true, FilterQuality = SKFilterQuality.High };
 							brush.UpdatePaint(paint, bounds);
 
-							return SKImageFilter.CreatePaint(paint, new SKImageFilter.CropRect(bounds));
+							return SKImageFilter.CreatePaint(paint, new(bounds));
 						}
 
 						return null;
@@ -454,6 +455,81 @@ half4 main()
 										return SKImageFilter.CreateArithmetic(multiplyAmount.Value, source1Amount.Value, source2Amount.Value, offset.Value, false, bgFilter, fgFilter, new(bounds));
 									}
 
+									return null;
+								}
+							case EffectType.ExposureEffect: // TODO: We can probably replace the pixel shader with a color matrix filter instead?
+								{
+									if (effectInterop.GetSourceCount() == 1 && effectInterop.GetPropertyCount() == 1 && effectInterop.GetSource(0) is IGraphicsEffectSource source)
+									{
+										SKImageFilter sourceFilter = GenerateEffectFilter(source, bounds);
+										if (sourceFilter is null)
+											return null;
+
+										effectInterop.GetNamedPropertyMapping("Exposure", out uint exposureProp, out _);
+
+										float exposure = (float)effectInterop.GetProperty(exposureProp);
+										float multiplier = MathF.Pow(2.0f, exposure);
+
+										string shader = $@"
+											uniform shader input;
+											uniform half multiplier;
+
+											half4 main() 
+											{{
+												half4 inputColor = sample(input);
+												return half4(inputColor.rgb * multiplier, inputColor.a);
+											}}
+										";
+
+										SKRuntimeEffect runtimeEffect = SKRuntimeEffect.Create(shader, out string errors);
+										if (errors is not null)
+											return null;
+
+										SKRuntimeEffectUniforms uniforms = new(runtimeEffect)
+										{
+											{ "multiplier", multiplier }
+										};
+										SKRuntimeEffectChildren children = new(runtimeEffect)
+										{
+											{ "input", null }
+										};
+
+										return SKImageFilter.CreateColorFilter(runtimeEffect.ToColorFilter(uniforms, children), sourceFilter, new(bounds));
+
+										// Reference (wuceffects.dll):
+										/*
+											void Windows::UI::Composition::ExposureEffectType::GenerateCode(const Windows::UI::Composition::EffectNode *node, Windows::UI::Composition::EffectGenerator *pGenerator, const char *pszOutputPixelName)
+											{
+												Windows::UI::Composition::StringBuilder *pStringBuilder;
+												std::string strInputPixel;
+												std::string strMultiplierProperty;
+												bool isPropertyDynamic;
+
+												strInputPixel = pGenerator->GetInputPixelName(node, 0);
+
+												isPropertyDynamic = node->IsPropertyDynamic(0); // ExposureValue
+												pGenerator->DeclareShaderVariable(
+													&strMultiplierProperty,
+													DCOMPOSITION_EXPRESSION_TYPE_SCALAR,
+													"Multiplier",
+													isPropertyDynamic,
+													[](void** defaultProperties, void** output) { *(float*)*output = pow(2.0, *(float*)(defaultProperties[0])); }
+												);
+  
+												pStringBuilder = pGenerator->BeginPSLine();
+												pStringBuilder->(pszOutputPixelName);
+												pStringBuilder->(" = minfloat4(");
+												pStringBuilder->(strInputPixel.c_str(), strInputPixel.size());
+												pStringBuilder->(".rgb * ");
+												pStringBuilder->(strMultiplierProperty.c_str(), strMultiplierProperty.size());
+												pStringBuilder->(", ");
+												pStringBuilder->(strInputPixel.c_str(), strInputPixel.size());
+												pStringBuilder->(".a);");
+												pStringBuilder->('\n');
+											}
+										*/
+									}
+
 									return null;
 								}
 							case EffectType.Unsupported: