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dropshadow.md

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-api-id -api-type
T:Windows.UI.Composition.DropShadow
winrt class

Windows.UI.Composition.DropShadow

-description

A drop shadow cast by a SpriteVisual or LayerVisual.

-remarks

DropShadows are a common way to provide an indication of depth in application UI. To add a DropShadow, create an instance of DropShadow and attach it using the .Shadow property on a SpriteVisual or LayerVisual.

Shadows are not clipped by the implicit clip set on the visual (based on size of the visual). However, shadows respect the explicit clip set on the visual using SpriteVisual.Clip Property.

Version history

Windows version SDK version Value added
1709 16299 SourcePolicy

-examples

Simple DropShadow

private async void InitComposition()
{
  _compositor = ElementCompositionPreview.GetElementVisual(MyGrid).Compositor;
  _imageLoader = ImageLoaderFactory.CreateImageLoader(_compositor);

  //Create surface brush and load image
  CompositionSurfaceBrush surfaceBrush = _compositor.CreateSurfaceBrush();
  surfaceBrush.Surface = await _imageLoader.LoadImageFromUriAsync(new Uri("ms-appx:///Assets/cat.jpg"));

  //Create sprite visual
  SpriteVisual visual = _compositor.CreateSpriteVisual();
  visual.Brush = surfaceBrush;
  visual.Size = new Vector2(270, 200);

  //Create drop shadow
  DropShadow shadow = _compositor.CreateDropShadow();
  shadow.BlurRadius = 5;
  shadow.Offset = new Vector3(15, 15, -10);
  shadow.Color = Colors.DarkGray;

  //Associate shadow with visual
  visual.Shadow = shadow;
}

DropShadow with Animations

private async void InitComposition()
{
  _compositor = ElementCompositionPreview.GetElementVisual(MyGrid).Compositor;
  _imageLoader = ImageLoaderFactory.CreateImageLoader(_compositor);

  //Create surface brush and load image
  CompositionSurfaceBrush surfaceBrush = _compositor.CreateSurfaceBrush();
  surfaceBrush.Surface = await _imageLoader.LoadImageFromUriAsync(new Uri("ms-appx:///Assets/cat.jpg"));

  //Create sprite visual
  SpriteVisual visual = _compositor.CreateSpriteVisual();
  visual.Brush = surfaceBrush;
  visual.Size = new Vector2(270, 200);

  //Create drop shadow
  DropShadow shadow = _compositor.CreateDropShadow();
  shadow.BlurRadius = 5;
  shadow.Offset = new Vector3(15, 15, -10);
  shadow.Color = Colors.DarkGray;

  //Create animations
  ScalarKeyFrameAnimation blurAnimation = this.CreateBlurAnimation();
  Vector3KeyFrameAnimation offsetAnimation = this.CreateOffsetAnimation();

  //Apply animations
  shadow.StartAnimation("BlurRadius", blurAnimation);
  shadow.StartAnimation("Offset", offsetAnimation);

  //Associate shadow with visual
  visual.Shadow = shadow;
}

private ScalarKeyFrameAnimation CreateBlurAnimation()
{
  ScalarKeyFrameAnimation shadowBlurAnimation = _compositor.CreateScalarKeyFrameAnimation();
  shadowBlurAnimation.InsertKeyFrame(0.0f, 5.0f);
  shadowBlurAnimation.InsertKeyFrame(0.5f, 20.0f);
  shadowBlurAnimation.InsertKeyFrame(1.0f, 5.0f);
  shadowBlurAnimation.Duration = TimeSpan.FromSeconds(2);
  shadowBlurAnimation.IterationBehavior = AnimationIterationBehavior.Forever;

  return shadowBlurAnimation;
}

private Vector3KeyFrameAnimation CreateOffsetAnimation()
{
  Vector3 startOffset = new Vector3(15, 15, -10);
  Vector3 endOffset = new Vector3(30, 30, -20);

  Vector3KeyFrameAnimation offsetAnimation = _compositor.CreateVector3KeyFrameAnimation();
  offsetAnimation.InsertKeyFrame(0.0f, startOffset);
  offsetAnimation.InsertKeyFrame(0.5f, endOffset);
  offsetAnimation.InsertKeyFrame(1.0f, startOffset);
  offsetAnimation.Duration = TimeSpan.FromSeconds(2);
  offsetAnimation.IterationBehavior = AnimationIterationBehavior.Forever;

  return offsetAnimation;
}

DropShadow using CompositionDropShadowSourcePolicy to inherit alpha from the Visual's brush

private async void InitComposition()
{
  _compositor = ElementCompositionPreview.GetElementVisual(MyGrid).Compositor;

  //Create surface brush and load image
  CompositionSurfaceBrush surfaceBrush = _compositor.CreateSurfaceBrush();
  surfaceBrush.Surface = LoadedImageSurface.StartLoadFromUri(new Uri("ms-appx:///Assets/circle.png"));

  //Create sprite visual
  SpriteVisual visual = _compositor.CreateSpriteVisual();
  visual.Brush = surfaceBrush;
  visual.Size = new Vector2(270, 200);

  //Create drop shadow
  DropShadow shadow = _compositor.CreateDropShadow();
  shadow.BlurRadius = 5;
  shadow.Offset = new Vector3(15, 15, -10);
  shadow.Color = Colors.DarkGray;

  //Specify mask policy for shadow
  shadow.SourcePolicy = CompositionDropShadowSourcePolicy.InheritFromVisualContent;

  //Associate shadow with visual
  visual.Shadow = shadow;
}

-see-also

CompositionShadow, IClosable