OpenStreetMapDataProvider.GetMapSizeInPixels(Double) Method

Returns the map size (in pixels) for the specified zoom level.

Namespace: DevExpress.XtraMap

Assembly: DevExpress.XtraMap.v18.2.dll

Declaration

C#

public override MapSize GetMapSizeInPixels(
    double zoomLevel
)

VB.NET

Public Overrides Function GetMapSizeInPixels(
    zoomLevel As Double
) As MapSize

Parameters

Name	Type	Description
zoomLevel	Double	A double value that specifies the zoom level.

Returns

Type	Description
MapSize	A MapSize object that is the map size.

Example

This example illustrates how to implement a custom provider for image tiles. To do this, it is necessary to create a MapDataProviderBase class descendant and assign it to the ImageLayer.DataProvider property.

The sample below shows how to load image tiles from a local cache. This is possible only if you previously downloaded a group of image tiles from one of the available image tile providers. For example, a list of alternative OpenStreetMap image tile providers is available here: OpenStreetMap: Tile usage policy.

Note

If you don’t need to create a custom data provider and only require changing the Uri to the location of image tiles, use the OpenStreetMapDataProvider.TileUriTemplate property.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-load-image-tiles-from-another-source-by-creating-custom-data-provider-e4758

Form1.cs

using System;
using System.Windows.Forms;
using DevExpress.XtraMap;
using System.IO;
using System.Drawing;
using System.Diagnostics;

namespace CustomProvider {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {
            // Create a map control, set its dock style and add it to the form.
            MapControl map = new MapControl();
            map.Dock = DockStyle.Fill;
            this.Controls.Add(map);

            // Create a layer to load image tiles from a local map data provider.
            ImageLayer imageTilesLayer = new ImageLayer();
            map.Layers.Add(imageTilesLayer);
            imageTilesLayer.DataProvider = new LocalProvider();

        }

        public class LocalProvider : MapDataProviderBase {

            readonly SphericalMercatorProjection projection = new SphericalMercatorProjection();

            public LocalProvider() {
                TileSource = new LocalTileSource(this);
            }

            public override ProjectionBase Projection {
                get {
                    return projection;
                }
            }

            public override MapSize GetMapSizeInPixels(double zoomLevel) {
                double imageSize;
                imageSize = LocalTileSource.CalculateTotalImageSize(zoomLevel);
                return new MapSize(imageSize, imageSize);
            }
            protected override Size BaseSizeInPixels {
                get { return new Size(Convert.ToInt32(LocalTileSource.tileSize * 2), Convert.ToInt32(LocalTileSource.tileSize * 2)); }
            }
        }

        public class LocalTileSource : MapTileSourceBase {
            public const int tileSize = 256;
            public const int maxZoomLevel = 2;
            string directoryPath;

            internal static double CalculateTotalImageSize(double zoomLevel) {
                if (zoomLevel < 1.0)
                    return zoomLevel * tileSize * 2;
                return Math.Pow(2.0, zoomLevel) * tileSize;
            }

            public LocalTileSource(ICacheOptionsProvider cacheOptionsProvider) :
                base((int)CalculateTotalImageSize(maxZoomLevel), (int)CalculateTotalImageSize(maxZoomLevel), tileSize, tileSize, cacheOptionsProvider) {
                DirectoryInfo dir = new DirectoryInfo(Directory.GetCurrentDirectory());
                directoryPath = dir.Parent.Parent.FullName;
            }

            public override Uri GetTileByZoomLevel(int zoomLevel, int tilePositionX, int tilePositionY) {
                if (zoomLevel <= maxZoomLevel) {
                    Uri u = new Uri(string.Format("file://" + directoryPath + "\\openstreetmap.org\\Hybrid_{0}_{1}_{2}.png", zoomLevel, tilePositionX, tilePositionY));
                    return u;
                }
                return null;
            }
        }
    }
}

Form1.vb

Imports System
Imports System.Windows.Forms
Imports DevExpress.XtraMap
Imports System.IO
Imports System.Drawing
Imports System.Diagnostics

Namespace CustomProvider
    Partial Public Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
            ' Create a map control, set its dock style and add it to the form.
            Dim map As New MapControl()
            map.Dock = DockStyle.Fill
            Me.Controls.Add(map)

            ' Create a layer to load image tiles from a local map data provider.
            Dim imageTilesLayer As New ImageLayer()
            map.Layers.Add(imageTilesLayer)
            imageTilesLayer.DataProvider = New LocalProvider()

        End Sub

        Public Class LocalProvider
            Inherits MapDataProviderBase


            Private ReadOnly projection_Renamed As New SphericalMercatorProjection()

            Public Sub New()
                TileSource = New LocalTileSource(Me)
            End Sub

            Public Overrides ReadOnly Property Projection() As ProjectionBase
                Get
                    Return projection_Renamed
                End Get
            End Property

            Public Overrides Function GetMapSizeInPixels(ByVal zoomLevel As Double) As MapSize
                Dim imageSize As Double
                imageSize = LocalTileSource.CalculateTotalImageSize(zoomLevel)
                Return New MapSize(imageSize, imageSize)
            End Function
            Protected Overrides ReadOnly Property BaseSizeInPixels() As Size
                Get
                    Return New Size(Convert.ToInt32(LocalTileSource.tileSize * 2), Convert.ToInt32(LocalTileSource.tileSize * 2))
                End Get
            End Property
        End Class

        Public Class LocalTileSource
            Inherits MapTileSourceBase

            Public Const tileSize As Integer = 256
            Public Const maxZoomLevel As Integer = 2
            Private directoryPath As String

            Friend Shared Function CalculateTotalImageSize(ByVal zoomLevel As Double) As Double
                If zoomLevel < 1.0 Then
                    Return zoomLevel * tileSize * 2
                End If
                Return Math.Pow(2.0, zoomLevel) * tileSize
            End Function

            Public Sub New(ByVal cacheOptionsProvider As ICacheOptionsProvider)
                MyBase.New(CInt((CalculateTotalImageSize(maxZoomLevel))), CInt((CalculateTotalImageSize(maxZoomLevel))), tileSize, tileSize, cacheOptionsProvider)
                Dim dir As New DirectoryInfo(Directory.GetCurrentDirectory())
                directoryPath = dir.Parent.Parent.FullName
            End Sub

            Public Overrides Function GetTileByZoomLevel(ByVal zoomLevel As Integer, ByVal tilePositionX As Integer, ByVal tilePositionY As Integer) As Uri
                If zoomLevel <= maxZoomLevel Then
                    Dim u As New Uri(String.Format("file://" & directoryPath & "\openstreetmap.org\Hybrid_{0}_{1}_{2}.png", zoomLevel, tilePositionX, tilePositionY))
                    Return u
                End If
                Return Nothing
            End Function
        End Class
    End Class
End Namespace