How to: Customize the Cylindrical Equal-Area Projection

• Jul 26, 2018
• 2 minutes to read

To customize equal-area projection, do the following.

• Set an EqualAreaProjection object to the MapItemsLayerBase.MapProjection property of a vector data layer.
• Specify its Width/Height ratio. To do this, assign this ratio based size to the MapItemsLayerBase.InitialMapSize property of the vector data layer.

Note

A complete sample project is available at: https://github.com/DevExpress-Examples/how-to-customize-cylindrical-equal-area-projection-t196064

XAML

<Page xmlns:Map="using:DevExpress.UI.Xaml.Map" 
    x:Class="MapControl_CustomProjections.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MapControl_CustomProjections"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" Loaded="Page_Loaded">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Map:MapControl x:Name="mapControl">
            <Map:VectorFileLayer>
                <Map:ShapefileReader>
                    <Map:MapPackageFileSource FileName="Assets\Countries.shp"/>
                </Map:ShapefileReader>
            </Map:VectorFileLayer>
        </Map:MapControl>
        <ListView Name="listView"
                  HorizontalAlignment="Right" VerticalAlignment="Top" 
                  Header="Projection Ratio:"
                  ItemsSource="{Binding ProjectionRatios}" 
                  FontSize="26.667" Margin="20" BorderThickness="2" BorderBrush="White"
                  MinWidth="250"
                  SelectionChanged="ListView_SelectionChanged">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}" TextAlignment="Left" Margin="8" />
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

    </Grid>
</Page>

C#

using DevExpress.UI.Xaml.Map;
using Windows.Foundation;
using Windows.UI.Xaml.Controls;

namespace MapControl_CustomProjections
{
    public sealed partial class MainPage : Page
    {
        ProjectionRatio[] projectionRatios = { 
                                                 new ProjectionRatio("Lambert", 3.14),
                                                 new ProjectionRatio("Behrmann", 2.36),
                                                 new ProjectionRatio("Trystan Edwards", 2),
                                                 new ProjectionRatio("Gall-Peters", 1.57),
                                                 new ProjectionRatio("Balthasart", 1.3),
                                                 new ProjectionRatio("Default", 1)
                                             };

        int sizeValue = 512;

        public  ProjectionRatio[] ProjectionRatios{ get { return projectionRatios; } }

        public MainPage()
        {
            this.InitializeComponent();
            this.DataContext = this;
        }

        private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e) {
            ListView listView = sender as ListView;
            if (listView == null) return;

            ((VectorFileLayer)mapControl.Layers[0]).InitialMapSize = new Size(
                ((ProjectionRatio)listView.SelectedItem).Value * sizeValue, sizeValue
            );
        }

        private void Page_Loaded(object sender, Windows.UI.Xaml.RoutedEventArgs e) {
            listView.SelectedIndex = ProjectionRatios.Length - 1;
        }
    }

    public class ProjectionRatio {
        public ProjectionRatio(string name, double value) {
            Name = name;
            Value = value;
        }

        public string Name { get; set; }
        public double Value { get; set; }
    }
}

VB.NET

Imports DevExpress.UI.Xaml.Map

Public NotInheritable Class MainPage
    Inherits Page

    Private projectionRatios() As ProjectionRatio = { _
        New ProjectionRatio("Lambert", 3.14), _
        New ProjectionRatio("Behrmann", 2.36), _
        New ProjectionRatio("Trystan Edwards", 2), _
        New ProjectionRatio("Gall-Peters", 1.57), _
        New ProjectionRatio("Balthasart", 1.3), _
        New ProjectionRatio("Default", 1) _
    }

    Private sizeValue As Integer = 512

    Public ReadOnly Property Ratios() As ProjectionRatio()
        Get
            Return projectionRatios
        End Get
    End Property

    Public Sub New()
        Me.InitializeComponent()
    End Sub

    Private Sub ListView_SelectionChanged(sender As Object, e As SelectionChangedEventArgs)
        Dim lView = TryCast(sender, ListView)
        If lView Is Nothing Then Return

        Dim vectorLayer = TryCast(map.Layers(0), VectorFileLayer)
        vectorLayer.InitialMapSize = New Size(Ratios(lView.SelectedIndex).Value * sizeValue, sizeValue)
    End Sub

    Private Sub Page_Loaded(sender As Object, e As RoutedEventArgs)
        Me.DataContext = Me
        listView.SelectedIndex = Ratios.Length - 1
    End Sub
End Class
Public Class ProjectionRatio
    Public Sub New(name As String, value As String)
        Me.Name = name
        Me.Value = value
    End Sub

    Public Property Name() As String
    Public Property Value() As Double
End Class