Convex Hull

This sample demonstrates using the ArcGIS Runtime SDK for WPF to perform a geometry operation to display a convex hull graphic. A convex hull is the smallest polygon that completely encases a set (i.e. locus) of points.

To use the sample, add 3 or more points on the map and click the Generate Convex Hull button. A polygon containing all the points entered will be returned.

XAML

<UserControl x:Class="ArcGISWPFSDK.LocalConvexHull"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:esri="http://schemas.esri.com/arcgis/client/2009">
    <Grid x:Name="LayoutRoot">

        <Grid.Resources>
            <esri:SimpleMarkerSymbol x:Key="DefaultMarkerSymbol" Color="Red" Size="6" />
            <esri:SimpleFillSymbol x:Key="DefaultFillSymbol" Fill="#88FFFF00" BorderBrush="Yellow" />
            <LinearGradientBrush x:Key="PanelGradient" EndPoint="0.5,1" StartPoint="0.5,0">
                <LinearGradientBrush.RelativeTransform>
                    <TransformGroup>
                        <ScaleTransform CenterY="0.5" CenterX="0.5"/>
                        <SkewTransform CenterY="0.5" CenterX="0.5"/>
                        <RotateTransform Angle="176" CenterY="0.5" CenterX="0.5"/>
                        <TranslateTransform/>
                    </TransformGroup>
                </LinearGradientBrush.RelativeTransform>
                <GradientStop Color="#FF145787" Offset="0.16"/>
                <GradientStop Color="#FF3D7FAC" Offset="0.502"/>
                <GradientStop Color="#FF88C5EF" Offset="0.984"/>
            </LinearGradientBrush>
        </Grid.Resources>

        <esri:Map x:Name="MyMap" Extent="-15000000,2000000,-7000000,8000000" Background="#FFE3E3E3">
            <esri:ArcGISLocalTiledLayer ID="BaseMap" Path="..\\Data\\TPKs\\Topographic.tpk"/>
            <esri:GraphicsLayer ID="InputGraphicsLayer" x:Name="_inputGraphicsLayer"/>
            <esri:GraphicsLayer ID="ConvexHullGraphicsLayer" x:Name="_convexHullGraphicsLayer"/>
        </esri:Map>

        <Grid HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,10,10,0" >
            <Rectangle Fill="{StaticResource PanelGradient}" Stroke="Gray"  RadiusX="10" RadiusY="10" Margin="0,0,0,5" >
                <Rectangle.Effect>
                    <DropShadowEffect/>
                </Rectangle.Effect>
            </Rectangle>
            <Rectangle Fill="#FFFFFFFF" Stroke="DarkGray" RadiusX="5" RadiusY="5" Margin="10,10,10,15" />
            <StackPanel Orientation="Vertical" Margin="30,20,20,30" >
                <TextBlock x:Name="ResponseTextBlock" Text="Add 3 or more points on the map and click the Generate Convex Hull button.  A polygon containing all the points entered will be returned. "
                           Width="400" TextAlignment="Left"  TextWrapping="Wrap" Foreground="Black"/>
                <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" >
                    <Button Content="Generate Convex Hull" Margin="0,5,5,0" x:Name="ConvexButton" 
                             Click="ConvexButton_Click" IsEnabled="False" />
                </StackPanel>
            </StackPanel>
        </Grid>

    </Grid>
</UserControl>

C#

using System.Linq;
using System.Windows;
using System.Windows.Controls;
using ESRI.ArcGIS.Client;
using ESRI.ArcGIS.Client.Tasks;
using ESRI.ArcGIS.Client.Local;

namespace ArcGISWPFSDK
{
    public partial class LocalConvexHull : UserControl
    {
        private Draw _drawObject;
        GeometryService _geometryTask;

        public LocalConvexHull()
        {
            InitializeComponent();

            LocalGeometryService.GetServiceAsync(lgs =>
            {
                _geometryTask = new GeometryService();
                _geometryTask.Url = lgs.UrlGeometryService;
                _geometryTask.ConvexHullCompleted += GeometryService_ConvexHullCompleted;
                _geometryTask.Failed += GeometryService_Failed;
                _drawObject = new Draw(MyMap)
                {
                    DrawMode = DrawMode.Point,
                    IsEnabled = true
                };                           
            });

            MyMap.Layers.LayersInitialized += (s, e) =>
            {
                _drawObject.DrawComplete += DrawObject_DrawComplete;
            };
        }

        private void DrawObject_DrawComplete(object sender, DrawEventArgs args)
        {
            _convexHullGraphicsLayer.ClearGraphics();

            ESRI.ArcGIS.Client.Geometry.MapPoint point = args.Geometry as ESRI.ArcGIS.Client.Geometry.MapPoint;
            point.SpatialReference = MyMap.SpatialReference;
            Graphic graphic = new Graphic()
            {
                Symbol = LayoutRoot.Resources["DefaultMarkerSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol,
                Geometry = point
            };

            _inputGraphicsLayer.Graphics.Add(graphic);

            if (_inputGraphicsLayer.Graphics.Count >= 3)
                ConvexButton.IsEnabled = true;
        }

        private void ConvexButton_Click(object sender, RoutedEventArgs e)
        {
            ConvexButton.IsEnabled = false;
            _convexHullGraphicsLayer.ClearGraphics();
            _geometryTask.ConvexHullAsync(_inputGraphicsLayer.ToList());
        }

        void GeometryService_ConvexHullCompleted(object sender, GeometryEventArgs e)
        {
            Graphic graphic = new Graphic()
            {
                Symbol = LayoutRoot.Resources["DefaultFillSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol,
                Geometry = e.Result
            };
            _convexHullGraphicsLayer.Graphics.Add(graphic);

            ConvexButton.IsEnabled = true;
        }

        private void GeometryService_Failed(object sender, TaskFailedEventArgs e)
        {
            MessageBox.Show("Geometry Service error: " + e.Error);
        }
    }
}

VB.NET

Imports System.Linq
Imports System.Windows
Imports System.Windows.Controls
Imports ESRI.ArcGIS.Client
Imports ESRI.ArcGIS.Client.Tasks
Imports ESRI.ArcGIS.Client.Local

Namespace ArcGISWPFSDK
    Partial Public Class LocalConvexHull
        Inherits UserControl
        Private MyDrawObject As Draw
        Private outputGraphicsLayer As GraphicsLayer
        Private inputGraphicsLayer As GraphicsLayer
        Private geometryService As GeometryService

        Public Sub New()
            InitializeComponent()

            Dim localGeometryService As New LocalGeometryService()
            AddHandler localGeometryService.StartCompleted, AddressOf localGeometryService_StartCompleted
            localGeometryService.StartAsync()


            outputGraphicsLayer = TryCast(MyMap.Layers("ConvexHullGraphicsLayer"), GraphicsLayer)
            inputGraphicsLayer = TryCast(MyMap.Layers("InputGraphicsLayer"), GraphicsLayer)
        End Sub

        Private Sub MyDrawObject_DrawComplete(sender As Object, args As DrawEventArgs)
            outputGraphicsLayer.ClearGraphics()

            Dim point As ESRI.ArcGIS.Client.Geometry.MapPoint = TryCast(args.Geometry, ESRI.ArcGIS.Client.Geometry.MapPoint)
            point.SpatialReference = MyMap.SpatialReference
            Dim graphic As New Graphic() With { _
             .Symbol = TryCast(LayoutRoot.Resources("DefaultMarkerSymbol"), ESRI.ArcGIS.Client.Symbols.Symbol), _
             .Geometry = point _
            }

            inputGraphicsLayer.Graphics.Add(graphic)

            If inputGraphicsLayer.Graphics.Count >= 3 Then
                ConvexButton.IsEnabled = True
            End If
        End Sub

        Private Sub ConvexButton_Click(sender As Object, e As RoutedEventArgs)
            ConvexButton.IsEnabled = False
            outputGraphicsLayer.ClearGraphics()
            geometryService.ConvexHullAsync(inputGraphicsLayer.ToList())
        End Sub

        Private Sub GeometryService_ConvexHullCompleted(sender As Object, e As GeometryEventArgs)
            Dim graphic As New Graphic() With { _
             .Symbol = TryCast(LayoutRoot.Resources("DefaultFillSymbol"), ESRI.ArcGIS.Client.Symbols.Symbol), _
             .Geometry = e.Result _
            }
            outputGraphicsLayer.Graphics.Add(graphic)

            ConvexButton.IsEnabled = True
        End Sub

        Private Sub GeometryService_Failed(sender As Object, e As TaskFailedEventArgs)
            MessageBox.Show("Geometry Service error: " & Convert.ToString(e.[Error]))
        End Sub

        Private Sub localGeometryService_StartCompleted(sender As Object, e As ComponentModel.AsyncCompletedEventArgs)
            Dim lgs As LocalGeometryService = TryCast(sender, LocalGeometryService)
            geometryService = New GeometryService()
            geometryService.Url = lgs.UrlGeometryService
            AddHandler geometryService.ConvexHullCompleted, AddressOf GeometryService_ConvexHullCompleted
            AddHandler geometryService.Failed, AddressOf GeometryService_Failed
            MyDrawObject = New Draw(MyMap) With { _
             .DrawMode = DrawMode.Point, _
             .IsEnabled = True _
            }
            AddHandler MyDrawObject.DrawComplete, AddressOf MyDrawObject_DrawComplete
        End Sub

    End Class
End Namespace