Use composition layer and win2d to render an image at load time on a background thread and implicitly fade in when rendered

mainpage.xaml.cs

using Microsoft.Graphics.Canvas.UI.Composition;
using Robmikh.Util.CompositionImageLoader;
using System;
using System.Numerics;
using System.Threading;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.UI;
using Windows.UI.Composition;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Hosting;


namespace imageplay
{
    /// <summary>
    /// Use composition layer and win2d to render an image at load time on a background thread and implicitly fade in when rendered
    /// </summary>
    public sealed partial class MainPage : Page
    {
        Compositor _compositor;
        SpriteVisual _drawnVisual;
        CompositionDrawingSurface _surface;
        IImageLoader _loader;
        AutoResetEvent _event = new AutoResetEvent(false);

        public MainPage()
        {
            this.InitializeComponent();
            this.SizeChanged += MainPage_SizeChanged;

            _compositor = ElementCompositionPreview.GetElementVisual(this).Compositor;
            _drawnVisual = _compositor.CreateSpriteVisual();
            ElementCompositionPreview.SetElementChildVisual(foo, _drawnVisual);
            _drawnVisual.Opacity = 0;

            ImplicitAnimationCollection implicitAnimationCollection = _compositor.CreateImplicitAnimationCollection();
            implicitAnimationCollection["Opacity"] = CreateAnimation();
            _drawnVisual.ImplicitAnimations = implicitAnimationCollection;

            _loader = Robmikh.Util.CompositionImageLoader.ImageLoaderFactory.CreateImageLoader(_compositor);

            Task.Run(() =>
            {
                //Simulate long render
                _event.WaitOne(1000);
                _surface = _loader.CreateSurface(new Size(100, 100));

                _loader.DrawIntoSurface(_surface, (a, o) =>
                {
                    using (var session = CanvasComposition.CreateDrawingSession(a))
                    {
                        session.Clear(Colors.Red);
                    }
                });

                _drawnVisual.Brush = _compositor.CreateSurfaceBrush(_surface);
                _drawnVisual.Opacity = 1.0f;
            });
        }

        ScalarKeyFrameAnimation CreateAnimation()
        {
            var scaleKeyFrameAnimation = _compositor.CreateScalarKeyFrameAnimation();
            scaleKeyFrameAnimation.Target = "Opacity";
            scaleKeyFrameAnimation.InsertExpressionKeyFrame(1.0f, "this.FinalValue");
            scaleKeyFrameAnimation.Duration = TimeSpan.FromMilliseconds(400);
            return scaleKeyFrameAnimation;
        }

        private void MainPage_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            _drawnVisual.Size = new Vector2((float)e.NewSize.Width, (float)e.NewSize.Height);
        }
    }
}