XAML-Map-Control/MapControl/MapImageLayer.cs

// XAML Map Control - http://xamlmapcontrol.codeplex.com/
// Copyright © Clemens Fischer 2012-2013
// Licensed under the Microsoft Public License (Ms-PL)

using System;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Net;
using System.Threading;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;
using System.Windows.Threading;

namespace MapControl
{
    /// <summary>
    /// Map image overlay. Fills the entire viewport with a map image from a web request,
    /// for example from a Web Map Service (WMS).
    /// The request Uri is specified by the UriFormat property, which has {X} and {Y}
    /// format specifiers for the map width and height in pixels, and either
    /// {w},{s},{e},{n} for the bounding box in lat/lon (like for example EPSG:4326) or
    /// {W},{S},{E},{N} for the bounding box in meters (like for example EPSG:3857)
    /// </summary>
    public class MapImageLayer : MapPanel
    {
        private readonly DispatcherTimer updateTimer;
        private string uriFormat;
        private bool latLonBoundingBox;
        private bool imageIsValid;
        private bool updateInProgress;
        private int currentImageIndex;

        public MapImageLayer()
        {
            Children.Add(new MapImage { Opacity = 0d });
            Children.Add(new MapImage { Opacity = 0d });

            updateTimer = new DispatcherTimer { Interval = TileContainer.UpdateInterval };
            updateTimer.Tick += UpdateImage;
        }

        public string UriFormat
        {
            get { return uriFormat; }
            set
            {
                if (value != null)
                {
                    if (!(value.Contains("{X}") && value.Contains("{Y}")))
                    {
                        throw new ArgumentException("UriFormat must specify the requested image size by {X} and {Y}.");
                    }

                    if (value.Contains("{w}") && value.Contains("{s}") && value.Contains("{e}") && value.Contains("{n}"))
                    {
                        latLonBoundingBox = true;
                    }
                    else if (!(value.Contains("{W}") && value.Contains("{S}") && value.Contains("{E}") && value.Contains("{N}")))
                    {
                        throw new ArgumentException("UriFormat must specify a bounding box in meters by {W},{S},{E},{N} or as lat/lon by {w},{s},{e},{n}.");
                    }
                }

                uriFormat = value;

                if (ParentMap != null)
                {
                    UpdateImage(this, EventArgs.Empty);
                }
            }
        }

        protected override void OnViewportChanged()
        {
            base.OnViewportChanged();

            imageIsValid = false;
            updateTimer.Stop();
            updateTimer.Start();
        }

        protected virtual ImageSource GetImage(double west, double east, double south, double north, int width, int height)
        {
            ImageSource image = null;
            var uri = uriFormat.Replace("{X}", width.ToString()).Replace("{Y}", height.ToString());

            if (latLonBoundingBox)
            {
                uri = uri.
                    Replace("{w}", west.ToString(CultureInfo.InvariantCulture)).
                    Replace("{s}", south.ToString(CultureInfo.InvariantCulture)).
                    Replace("{e}", east.ToString(CultureInfo.InvariantCulture)).
                    Replace("{n}", north.ToString(CultureInfo.InvariantCulture));
            }
            else
            {
                var p1 = ParentMap.MapTransform.Transform(new Location(south, west));
                var p2 = ParentMap.MapTransform.Transform(new Location(north, east));
                var arc = TileSource.EarthRadius * Math.PI / 180d;

                uri = uri.
                    Replace("{W}", (arc * p1.X).ToString(CultureInfo.InvariantCulture)).
                    Replace("{S}", (arc * p1.Y).ToString(CultureInfo.InvariantCulture)).
                    Replace("{E}", (arc * p2.X).ToString(CultureInfo.InvariantCulture)).
                    Replace("{N}", (arc * p2.Y).ToString(CultureInfo.InvariantCulture));
            }

            try
            {
                var bitmap = new BitmapImage();
                var request = (HttpWebRequest)WebRequest.Create(uri);
                request.UserAgent = "XAML Map Control";

                using (var response = (HttpWebResponse)request.GetResponse())
                using (var responseStream = response.GetResponseStream())
                using (var memoryStream = new MemoryStream())
                {
                    responseStream.CopyTo(memoryStream);

                    bitmap.BeginInit();
                    bitmap.CacheOption = BitmapCacheOption.OnLoad;
                    bitmap.StreamSource = memoryStream;
                    bitmap.EndInit();
                    bitmap.Freeze();
                }

                image = bitmap;
            }
            catch (Exception ex)
            {
                Trace.TraceWarning("{0}: {1}", uri, ex.Message);
            }

            return image;
        }

        private void UpdateImage(object sender, EventArgs e)
        {
            updateTimer.Stop();

            if (updateInProgress || string.IsNullOrWhiteSpace(uriFormat))
            {
                return;
            }

            imageIsValid = true;
            updateInProgress = true;

            var loc1 = ParentMap.ViewportPointToLocation(new Point(0d, 0d));
            var loc2 = ParentMap.ViewportPointToLocation(new Point(ActualWidth, 0d));
            var loc3 = ParentMap.ViewportPointToLocation(new Point(0d, ActualHeight));
            var loc4 = ParentMap.ViewportPointToLocation(new Point(ActualWidth, ActualHeight));
            var width = (int)ActualWidth;
            var height = (int)ActualHeight;

            ThreadPool.QueueUserWorkItem(o =>
            {
                var west = Math.Min(loc1.Longitude, Math.Min(loc2.Longitude, Math.Min(loc3.Longitude, loc4.Longitude)));
                var east = Math.Max(loc1.Longitude, Math.Max(loc2.Longitude, Math.Max(loc3.Longitude, loc4.Longitude)));
                var south = Math.Min(loc1.Latitude, Math.Min(loc2.Latitude, Math.Min(loc3.Latitude, loc4.Latitude)));
                var north = Math.Max(loc1.Latitude, Math.Max(loc2.Latitude, Math.Max(loc3.Latitude, loc4.Latitude)));
                var image = GetImage(west, east, south, north, width, height);

                if (image != null)
                {
                    Dispatcher.BeginInvoke((Action)(() =>
                    {
                        var mapImage = (MapImage)Children[currentImageIndex];
                        mapImage.BeginAnimation(Image.OpacityProperty,
                            new DoubleAnimation
                            {
                                To = 0,
                                Duration = Tile.AnimationDuration,
                                BeginTime = Tile.AnimationDuration
                            });

                        currentImageIndex = (currentImageIndex + 1) % 2;
                        mapImage = (MapImage)Children[currentImageIndex];
                        mapImage.Source = null;
                        mapImage.North = double.NaN; // avoid frequent MapRectangle.UpdateGeometry() calls
                        mapImage.West = west;
                        mapImage.East = east;
                        mapImage.South = south;
                        mapImage.North = north;
                        mapImage.Source = image;
                        mapImage.BeginAnimation(Image.OpacityProperty, new DoubleAnimation(1d, Tile.AnimationDuration));

                        if (!imageIsValid)
                        {
                            UpdateImage(this, EventArgs.Empty);
                        }
                    }));
                }

                updateInProgress = false;
            });
        }
    }
}