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Lets start by looking at Bing Maps control. We are going to control map loading so we need to ensure that Map.Mode is set to MercatorMode. I have set the TileSource to a custom tile source.
<my:Map.Mode>
<myCore:MercatorMode></myCore:MercatorMode>
</my:Map.Mode>
<my:MapLayer x:Name="mlTiles">
<my:MapTileLayer>
<my:MapTileLayer.TileSources>
<locals:BingMapTileSource></locals:BingMapTileSource>
</my:MapTileLayer.TileSources>
</my:MapTileLayer>
</my:MapLayer>
now we define tile sources we are going to use. For this example, lets look at bing maps tile source. I have used this mechanism with OpenStreet, OSMRender, Google and Nokia maps as well.
public class BingMapTileSource : TileSource
{
public BingMapTileSource() : base("http://ecn.t2.tiles.virtualearth.net/tiles/r{quadkey}.png?g=838") { }
public override System.Uri GetUri(int x, int y, int zoomLevel)
{
OfflineTile ot = new OfflineTile(base.GetUri(x, y, zoomLevel), x, y, zoomLevel, TileSourceDef.OpenStreetMaps);
TileManager.EnqueueRequest(ot);
return null;
}
}
As you can see I have a uri for tile source. and I use that to create instance of OfflineTile class and I queue it up.
public enum TileSourceDef
{
Bing,
OpenStreetMaps,
}
public class OfflineTile
{
public string tilePath;
public Location location;
public bool Ready;
public OfflineTile(Uri sourceUri, int x, int y, int zoom, TileSourceDef tileSource)
{
double lat, lon;
TileSystem.TileXYToLatLong(x, y, zoom, out lat, out lon);
location = new Location() { Latitude = lat, Longitude = lon };
IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication();
string destDir = string.Format("/Offline/{0}", tileSource);
if (!isf.DirectoryExists(destDir))
isf.CreateDirectory(destDir);
string fileName = Path.Combine(destDir, String.Format("{0}.png", TileSystem.TileXYToQuadKey(x, y, zoom)));
tilePath = fileName;
if (!isf.FileExists(fileName))
{
WebClient wc = new WebClient();
wc.OpenReadCompleted += (s, ev) =>
{
if (ev.Error == null)
{
using (IsolatedStorageFileStream output = isf.OpenFile(fileName, FileMode.OpenOrCreate))
ev.Result.CopyTo(output);
this.Ready = true;
}
};
wc.OpenReadAsync(sourceUri);
}
else
{
this.Ready = true;
}
}
public Image GetTileImage()
{
IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication();
BitmapImage bi = new BitmapImage();
bi.SetSource(isf.OpenFile(this.tilePath, FileMode.Open, FileAccess.Read));
return new Image() { Source = bi, Height = bi.PixelHeight, Width = bi.PixelWidth };
}
}
I use another class to translate from X, Y and Z to Latitude and Longitude. There where TileSystem comes into play. I found this in one of the msdn samples and I added just 1 method to it. The method is TileSystem.TileXYToLatLong. In the tile source, the map already passes X, Y. Took me a while to figure out that it was TileX and TileY and that I needed to use Latitude and Longitudes when inserting the tile image. As you can see I used methods already present in the class to do the dirty work 🙂
static class TileSystem
{
private const double EarthRadius = 6378137;
private const double MinLatitude = -85.05112878;
private const double MaxLatitude = 85.05112878;
private const double MinLongitude = -180;
private const double MaxLongitude = 180;
/// <summary>
/// Clips a number to the specified minimum and maximum values.
/// </summary>
/// <param name="n">The number to clip.</param>
/// <param name="minValue">Minimum allowable value.</param>
/// <param name="maxValue">Maximum allowable value.</param>
/// <returns>The clipped value.</returns>
private static double Clip(double n, double minValue, double maxValue)
{
return Math.Min(Math.Max(n, minValue), maxValue);
}
/// <summary>
/// Determines the map width and height (in pixels) at a specified level
/// of detail.
/// </summary>
/// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)
/// to 23 (highest detail).</param>
/// <returns>The map width and height in pixels.</returns>
public static uint MapSize(int levelOfDetail)
{
return (uint)256 << levelOfDetail;
}
/// <summary>
/// Determines the ground resolution (in meters per pixel) at a specified
/// latitude and level of detail.
/// </summary>
/// <param name="latitude">Latitude (in degrees) at which to measure the
/// ground resolution.</param>
/// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)
/// to 23 (highest detail).</param>
/// <returns>The ground resolution, in meters per pixel.</returns>
public static double GroundResolution(double latitude, int levelOfDetail)
{
latitude = Clip(latitude, MinLatitude, MaxLatitude);
return Math.Cos(latitude * Math.PI / 180) * 2 * Math.PI * EarthRadius / MapSize(levelOfDetail);
}
/// <summary>
/// Determines the map scale at a specified latitude, level of detail,
/// and screen resolution.
/// </summary>
/// <param name="latitude">Latitude (in degrees) at which to measure the
/// map scale.</param>
/// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)
/// to 23 (highest detail).</param>
/// <param name="screenDpi">Resolution of the screen, in dots per inch.</param>
/// <returns>The map scale, expressed as the denominator N of the ratio 1 : N.</returns>
public static double MapScale(double latitude, int levelOfDetail, int screenDpi)
{
return GroundResolution(latitude, levelOfDetail) * screenDpi / 0.0254;
}
/// <summary>
/// Converts a point from latitude/longitude WGS-84 coordinates (in degrees)
/// into pixel XY coordinates at a specified level of detail.
/// </summary>
/// <param name="latitude">Latitude of the point, in degrees.</param>
/// <param name="longitude">Longitude of the point, in degrees.</param>
/// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)
/// to 23 (highest detail).</param>
/// <param name="pixelX">Output parameter receiving the X coordinate in pixels.</param>
/// <param name="pixelY">Output parameter receiving the Y coordinate in pixels.</param>
public static void LatLongToPixelXY(double latitude, double longitude, int levelOfDetail, out int pixelX, out int pixelY)
{
latitude = Clip(latitude, MinLatitude, MaxLatitude);
longitude = Clip(longitude, MinLongitude, MaxLongitude);
double x = (longitude + 180) / 360;
double sinLatitude = Math.Sin(latitude * Math.PI / 180);
double y = 0.5 - Math.Log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);
uint mapSize = MapSize(levelOfDetail);
pixelX = (int)Clip(x * mapSize + 0.5, 0, mapSize - 1);
pixelY = (int)Clip(y * mapSize + 0.5, 0, mapSize - 1);
}
/// <summary>
/// Converts a pixel from pixel XY coordinates at a specified level of detail
/// into latitude/longitude WGS-84 coordinates (in degrees).
/// </summary>
/// <param name="pixelX">X coordinate of the point, in pixels.</param>
/// <param name="pixelY">Y coordinates of the point, in pixels.</param>
/// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)
/// to 23 (highest detail).</param>
/// <param name="latitude">Output parameter receiving the latitude in degrees.</param>
/// <param name="longitude">Output parameter receiving the longitude in degrees.</param>
public static void PixelXYToLatLong(int pixelX, int pixelY, int levelOfDetail, out double latitude, out double longitude)
{
double mapSize = MapSize(levelOfDetail);
double x = (Clip(pixelX, 0, mapSize - 1) / mapSize) - 0.5;
double y = 0.5 - (Clip(pixelY, 0, mapSize - 1) / mapSize);
latitude = 90 - 360 * Math.Atan(Math.Exp(-y * 2 * Math.PI)) / Math.PI;
longitude = 360 * x;
}
/// <summary>
/// Converts pixel XY coordinates into tile XY coordinates of the tile containing
/// the specified pixel.
/// </summary>
/// <param name="pixelX">Pixel X coordinate.</param>
/// <param name="pixelY">Pixel Y coordinate.</param>
/// <param name="tileX">Output parameter receiving the tile X coordinate.</param>
/// <param name="tileY">Output parameter receiving the tile Y coordinate.</param>
public static void PixelXYToTileXY(int pixelX, int pixelY, out int tileX, out int tileY)
{
tileX = pixelX / 256;
tileY = pixelY / 256;
}
/// <summary>
/// Converts tile XY coordinates into pixel XY coordinates of the upper-left pixel
/// of the specified tile.
/// </summary>
/// <param name="tileX">Tile X coordinate.</param>
/// <param name="tileY">Tile Y coordinate.</param>
/// <param name="pixelX">Output parameter receiving the pixel X coordinate.</param>
/// <param name="pixelY">Output parameter receiving the pixel Y coordinate.</param>
public static void TileXYToPixelXY(int tileX, int tileY, out int pixelX, out int pixelY)
{
pixelX = tileX * 256;
pixelY = tileY * 256;
}
public static void TileXYToLatLong(int tileX, int tileY, int zoomLevel, out double latitude, out double longitude)
{
int pixelX;
int pixelY;
TileXYToPixelXY(tileX, tileY, out pixelX, out pixelY);
PixelXYToLatLong(pixelX, pixelY, zoomLevel, out latitude, out longitude);
}
/// <summary>
/// Converts tile XY coordinates into a QuadKey at a specified level of detail.
/// </summary>
/// <param name="tileX">Tile X coordinate.</param>
/// <param name="tileY">Tile Y coordinate.</param>
/// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)
/// to 23 (highest detail).</param>
/// <returns>A string containing the QuadKey.</returns>
public static string TileXYToQuadKey(int tileX, int tileY, int levelOfDetail)
{
StringBuilder quadKey = new StringBuilder();
for (int i = levelOfDetail; i > 0; i--)
{
char digit = '0';
int mask = 1 << (i - 1);
if ((tileX & mask) != 0)
{
digit++;
}
if ((tileY & mask) != 0)
{
digit++;
digit++;
}
quadKey.Append(digit);
}
return quadKey.ToString();
}
/// <summary>
/// Converts a QuadKey into tile XY coordinates.
/// </summary>
/// <param name="quadKey">QuadKey of the tile.</param>
/// <param name="tileX">Output parameter receiving the tile X coordinate.</param>
/// <param name="tileY">Output parameter receiving the tile Y coordinate.</param>
/// <param name="levelOfDetail">Output parameter receiving the level of detail.</param>
public static void QuadKeyToTileXY(string quadKey, out int tileX, out int tileY, out int levelOfDetail)
{
tileX = tileY = 0;
levelOfDetail = quadKey.Length;
for (int i = levelOfDetail; i > 0; i--)
{
int mask = 1 << (i - 1);
switch (quadKey[levelOfDetail - i])
{
case '0':
break;
case '1':
tileX |= mask;
break;
case '2':
tileY |= mask;
break;
case '3':
tileX |= mask;
tileY |= mask;
break;
default:
throw new ArgumentException("Invalid QuadKey digit sequence.");
}
}
\ }
}
Finally lets see what actually happens to the queued tile. All it does is spawn off the request using ThreadPool
public class TileManager
{
static Queue<OfflineTile> requestQueue = new Queue<OfflineTile>();
public static Queue<OfflineTile> ResponseQueue = new Queue<OfflineTile>();
static ManualResetEvent waitEvent;
static volatile bool WaitWhileProcessing = false;
public static void Initialise(ManualResetEvent mreWait)
{
waitEvent = mreWait;
}
public static void EnqueueRequest(OfflineTile ot)
{
requestQueue.Enqueue(ot);
if (!WaitWhileProcessing)
{
WaitWhileProcessing = true;
ThreadPool.QueueUserWorkItem(ProcessTiles);
}
}
public static void ProcessTiles(Object stateInfo)
{
waitEvent.Set();
while (requestQueue.Count > 0)
{
OfflineTile t = requestQueue.Peek();
if (t.Ready)
{
t = requestQueue.Dequeue();
//Dispatcher.BeginInvoke(() => mapLayer.AddChild(t.TileBitmap, new System.Device.Location.GeoCoordinate(t.y, t.X)));
ResponseQueue.Enqueue(t);
}
else
Thread.Sleep(10);
}
waitEvent.Reset();
WaitWhileProcessing = false;
}
}
Now in the code behind this is what I do. I spawn off another thread that monitors for any available tiles and adds them to UI.
ManualResetEvent mrt = new ManualResetEvent(false);
Thread t = null;
private void ManageMapTiles()
{
while (true)
{
App.WaitEvent.WaitOne(10);
if (TileManager.ResponseQueue.Count > 0)
{
OfflineTile ot = TileManager.ResponseQueue.Dequeue();
Dispatcher.BeginInvoke(() => this.SetTile(ot));
}
}
}
private object lockobj = new object();
private void SetTile(OfflineTile ot)
{
lock (lockobj)
{
IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication();
BitmapImage bi = new BitmapImage();
bi.SetSource(isf.OpenFile(ot.tilePath, FileMode.Open, FileAccess.Read));
Image img = new Image() { Source = bi, Height = bi.PixelHeight, Width = bi.PixelWidth, Opacity = 1, Stretch = System.Windows.Media.Stretch.None };
mlTiles.AddChild(img, new GeoCoordinate(ot.location.Latitude, ot.location.Longitude));
}
}
private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
{
t = new Thread(new ThreadStart(ManageMapTiles));
t.Start();
watcher = new GeoCoordinateWatcher(GeoPositionAccuracy.High);
watcher.MovementThreshold = 10;
watcher.StatusChanged += new EventHandler<GeoPositionStatusChangedEventArgs>(watcher_StatusChanged);
watcher.PositionChanged += new EventHandler<GeoPositionChangedEventArgs<GeoCoordinate>>(watcher_PositionChanged);
// start up LocServ in bg; watcher_StatusChanged will be called when complete.
new Thread(startLocServInBackground).Start();
}
now let me just tell you there is much optimisation that can be done and I did for GoA2B..its a shame I never released it. Instead of just one tile layer, you need to have multiple map layers one for each zoom levels and you show / hide desired (depending upon zoom) the correct layer.
Invoke IT Limited 