Version 5.0: Separated map projection and view transform.

MapControl/Shared/ViewTransform.cs

@@ -0,0 +1,118 @@
+// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
+// © 2020 Clemens Fischer
+// Licensed under the Microsoft Public License (Ms-PL)
+
+#if WINDOWS_UWP
+using Windows.Foundation;
+using Windows.UI.Xaml.Media;
+#else
+using System.Windows;
+using System.Windows.Media;
+#endif
+
+namespace MapControl
+{
+    /// <summary>
+    /// Defines the transformation between cartesian map coordinates and viewport coordinates.
+    /// </summary>
+    public class ViewTransform
+    {
+        /// <summary>
+        /// Gets the transform matrix from cartesian map coordinates to viewport coordinates.
+        /// </summary>
+        public Matrix MapToViewMatrix { get; private set; }
+
+        /// <summary>
+        /// Gets the transform matrix from viewport coordinates to cartesian map coordinates.
+        /// </summary>
+        public Matrix ViewToMapMatrix { get; private set; }
+
+        /// <summary>
+        /// Gets the scaling factor from cartesian map coordinates to viewport coordinates.
+        /// </summary>
+        public double Scale { get; private set; }
+
+        /// <summary>
+        /// Gets the rotation angle of the transform matrix.
+        /// </summary>
+        public double Rotation { get; private set; }
+
+        /// <summary>
+        /// Transforms a Point from cartesian map coordinates to viewport coordinates.
+        /// </summary>
+        public Point MapToView(Point point)
+        {
+            return MapToViewMatrix.Transform(point);
+        }
+
+        /// <summary>
+        /// Transforms a Point from viewport coordinates to cartesian map coordinates.
+        /// </summary>
+        public Point ViewToMap(Point point)
+        {
+            return ViewToMapMatrix.Transform(point);
+        }
+
+        public void SetTransform(Point mapCenter, Point viewportCenter, double scale, double rotation)
+        {
+            Scale = scale;
+            Rotation = rotation;
+
+            var transform = new Matrix(Scale, 0d, 0d, -Scale, -Scale * mapCenter.X, Scale * mapCenter.Y);
+
+            transform.Rotate(Rotation);
+            transform.Translate(viewportCenter.X, viewportCenter.Y);
+
+            MapToViewMatrix = transform;
+
+            transform.Invert();
+
+            ViewToMapMatrix = transform;
+        }
+
+        public Matrix GetTileLayerTransform(double tileMatrixScale, Point tileMatrixTopLeft, Point tileMatrixOrigin)
+        {
+            var transformScale = Scale / tileMatrixScale;
+            var transform = new Matrix(transformScale, 0d, 0d, transformScale, 0d, 0d);
+
+            transform.Rotate(Rotation);
+
+            // tile matrix origin in map coordinates
+            //
+            var mapOrigin = new Point(
+                tileMatrixTopLeft.X + tileMatrixOrigin.X / tileMatrixScale,
+                tileMatrixTopLeft.Y - tileMatrixOrigin.Y / tileMatrixScale);
+
+            // tile matrix origin in viewport coordinates
+            //
+            var viewOrigin = MapToView(mapOrigin);
+
+            transform.Translate(viewOrigin.X, viewOrigin.Y);
+
+            return transform;
+        }
+
+        public Rect GetTileMatrixBounds(double tileMatrixScale, Point tileMatrixTopLeft, Size viewportSize)
+        {
+            var transformScale = tileMatrixScale / Scale;
+            var transform = new Matrix(transformScale, 0d, 0d, transformScale, 0d, 0d);
+
+            transform.Rotate(-Rotation);
+
+            // viewport origin in map coordinates
+            //
+            var origin = ViewToMap(new Point());
+
+            // translate origin to tile matrix origin in pixels
+            //
+            transform.Translate(
+                tileMatrixScale * (origin.X - tileMatrixTopLeft.X),
+                tileMatrixScale * (tileMatrixTopLeft.Y - origin.Y));
+
+            // transform viewport bounds to tile pixel bounds
+            //
+            return new MatrixTransform { Matrix = transform }
+                .TransformBounds(new Rect(0d, 0d, viewportSize.Width, viewportSize.Height));
+        }
+    }
+}