XAML-Map-Control/MapControl/ImageTileSource.WPF.cs

// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
// © 2017 Clemens Fischer
// Licensed under the Microsoft Public License (Ms-PL)

using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace MapControl
{
    /// <summary>
    /// Provides the image of a map tile. ImageTileSource bypasses image downloading
    /// and optional caching in TileImageLoader. By overriding the LoadImage method,
    /// an application can provide tile images from an arbitrary source.
    /// If the IsAsync property is true, LoadImage will be called from a separate,
    /// non-UI thread and must therefore return a frozen ImageSource.
    /// </summary>
    public class ImageTileSource : TileSource
    {
        public bool IsAsync { get; set; }

        public virtual ImageSource LoadImage(int x, int y, int zoomLevel)
        {
            ImageSource image = null;

            var uri = GetUri(x, y, zoomLevel);

            if (uri != null)
            {
                if (IsAsync)
                {
                    image = BitmapSourceHelper.FromUri(uri);
                }
                else
                {
                    image = new BitmapImage(uri);
                }
            }

            return image;
        }
    }
}