Create MapItemsImageLayer.WPF.cs

MapControl/WPF/MapItemsImageLayer.WPF.cs

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+// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
+// © 2020 Clemens Fischer
+// Licensed under the Microsoft Public License (Ms-PL)
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Media;
+
+namespace MapControl
+{
+    public interface IMapDrawingItem
+    {
+        IEnumerable<Location> Locations { get; }
+
+        Drawing GetDrawing(IList<Point> positions, double scale, double rotation);
+    }
+
+    public class MapItemsImageLayer : MapImageLayer
+    {
+        public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.Register(
+            nameof(ItemsSource), typeof(IEnumerable<IMapDrawingItem>), typeof(MapItemsImageLayer));
+
+        public IEnumerable<IMapDrawingItem> ItemsSource
+        {
+            get { return (IEnumerable<IMapDrawingItem>)GetValue(ItemsSourceProperty); }
+            set { SetValue(ItemsSourceProperty, value); }
+        }
+
+        protected override async Task<ImageSource> GetImageAsync()
+        {
+            ImageSource image = null;
+            var projection = ParentMap?.MapProjection;
+            var items = ItemsSource;
+
+            if (projection != null && items != null)
+            {
+                image = await Task.Run(() => GetImage(projection, items));
+            }
+
+            return image;
+        }
+
+        private ImageSource GetImage(MapProjection projection, IEnumerable<IMapDrawingItem> items)
+        {
+            var scale = ParentMap.ViewTransform.Scale;
+            var rotation = ParentMap.ViewTransform.Rotation;
+            var mapRect = projection.BoundingBoxToRect(BoundingBox);
+            var imageRect = new Rect(0, 0, scale * mapRect.Width, scale * mapRect.Height);
+            var drawings = new DrawingGroup();
+
+            foreach (var item in items)
+            {
+                var positions = item.Locations.Select(l => projection.LocationToMap(l)).ToList();
+
+                if (positions.Any(p => mapRect.Contains(p)))
+                {
+                    for (int i = 0; i < positions.Count; i++)
+                    {
+                        positions[i] = new Point(scale * (positions[i].X - mapRect.X),
+                              imageRect.Height - scale * (positions[i].Y - mapRect.Y));
+                    }
+
+                    drawings.Children.Add(item.GetDrawing(positions, scale, rotation));
+                }
+            }
+
+            var drawingBrush = new DrawingBrush
+            {
+                Drawing = drawings,
+                ViewboxUnits = BrushMappingMode.Absolute,
+                Viewbox = imageRect,
+            };
+
+            var drawing = new GeometryDrawing
+            {
+                Geometry = new RectangleGeometry(imageRect),
+                Brush = drawingBrush
+            };
+
+            var image = new DrawingImage(drawing);
+            image.Freeze();
+
+            return image;
+        }
+    }
+}