Compute Class Statistics

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Demonstrates how to compute class statistics for an image layer and display the results with the Maximum Likelihood Classification renderer rule.

"Desktop" "Store" "Phone" Available for Desktop, Store, Phone

Sample Code

<UserControl x:Class="ArcGISRuntime.Samples.Desktop.ComputeClassStatistics"
    <Grid x:Name="layoutGrid">
            <esri:SimpleFillSymbol  x:Key="FillSymbol" Color="#77FF9999">
                    <esri:SimpleLineSymbol Color="#FFFF9999" Style="Solid" Width="2" />

            <esri:SimpleRenderer x:Key="FillRenderer" Symbol="{StaticResource FillSymbol}" />

        <esri:MapView x:Name="MyMapView" WrapAround="True">
                <esri:ArcGISTiledMapServiceLayer ID="StreetMapLayer"
                    ServiceUri="" />

				<esri:ArcGISImageServiceLayer x:Name="imageLayer"
                    ServiceUri="" />

				<esri:GraphicsOverlay ID="graphicsOverlay" Renderer="{StaticResource FillRenderer}"/>

		<Border x:Name="uiPanel"
				Background="White" BorderBrush="Black" BorderThickness="1"
				HorizontalAlignment="Right" VerticalAlignment="Top"
				Margin="30" Padding="20"
				<TextBlock Text="Add two or more class definition points by clicking on the map. Then click the 'Compute Class Statistics' button to show the reclassified image."
                           Margin="12,0,12,0" TextWrapping="Wrap" />
                <StackPanel Margin="0,16,0,0" HorizontalAlignment="Center" Orientation="Horizontal">
                    <Button Content="Compute Class Statistics" Click="ComputeClassStatisticsButton_Click"
                            IsEnabled="{Binding ElementName=MyMapView, Path=Editor.IsActive}" />
                    <Button Content="Reset" Margin="12,0,0,0" Click="ResetButton_Click" />
                <ProgressBar x:Name="progress" IsIndeterminate="True" Margin="12,12,12,0" Visibility="Collapsed" />
using Esri.ArcGISRuntime.Controls;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Layers;
using Esri.ArcGISRuntime.Tasks.Imagery;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;

namespace ArcGISRuntime.Samples.Desktop
	/// <summary>
	/// Demonstrates how to compute class statistics for an image layer and display the results with the Maximum Likelihood Classification renderer rule.
	/// </summary>
	/// <title>Compute Class Statistics</title>
	/// <category>Tasks</category>
	/// <subcategory>Imagery</subcategory>
	public partial class ComputeClassStatistics : UserControl
		private ArcGISImageServiceLayer _imageLayer;
		private GraphicsOverlay _graphicsOverlay;

		/// <summary>Construct compute class statistics sample control</summary>
		public ComputeClassStatistics()

			_graphicsOverlay = MyMapView.GraphicsOverlays["graphicsOverlay"];
			MyMapView.LayerLoaded += MyMapView_LayerLoaded;

		// Zooms to the image layer and starts accepting user points
		private async void MyMapView_LayerLoaded(object sender, LayerLoadedEventArgs e)
			if (e.Layer is ArcGISImageServiceLayer)
				if (e.Layer.FullExtent != null)
					await MyMapView.SetViewAsync(e.Layer.FullExtent);

				_imageLayer = (ArcGISImageServiceLayer)e.Layer;
				await AcceptClassPointsAsync();

		// Computes Class Statistics for the image layer using user input graphics as class definition polygons
		private async void ComputeClassStatisticsButton_Click(object sender, RoutedEventArgs e)
				if (_graphicsOverlay.Graphics.Count < 2)
					throw new ArgumentException("Before computing statistics, enter two or more class definition areas by clicking the image on the map.");

				progress.Visibility = Visibility.Visible;
				if (MyMapView.Editor.IsActive)

				var statsTask = new ComputeClassStatisticsTask(new Uri(imageLayer.ServiceUri));

				var statsParam = new ComputeClassStatisticsParameters();
				statsParam.ClassDescriptions = _graphicsOverlay.Graphics
					.Select((g, idx) => new ClassDescription(idx, idx.ToString(), g.Geometry as Polygon)).ToList();

				var result = await statsTask.ComputeClassStatisticsAsync(statsParam);

				imageLayer.RenderingRule = new RenderingRule()
					RasterFunctionName = "MLClassify",
					VariableName = "Raster",
					RasterFunctionArguments = new Dictionary<string, object> { { "SignatureFile", result.GSG } },
			catch (Exception ex)
				MessageBox.Show(ex.Message, "Sample Error");
				progress.Visibility = Visibility.Collapsed;

		// Reset the rendering rule for the image layer and restart accepting loop
		private async void ResetButton_Click(object sender, RoutedEventArgs e)
			imageLayer.RenderingRule = null;
			await AcceptClassPointsAsync();

		// Continually accepts user-entered points
		// - Buffered polygons are created from the points and added to the graphics layer
		private async Task AcceptClassPointsAsync()
			// Get current viewpoints extent from the MapView
			var currentViewpoint = MyMapView.GetCurrentViewpoint(ViewpointType.BoundingGeometry);
			var viewpointExtent = currentViewpoint.TargetGeometry.Extent;
				while (true)

					var point = await MyMapView.Editor.RequestPointAsync();
					var polygon = GeometryEngine.Buffer(point, viewpointExtent.Width * .01);
					var attr = new Dictionary<string, object>() { { "ID", _graphicsOverlay.Graphics.Count + 1 } };
					_graphicsOverlay.Graphics.Add(new Graphic(polygon, attr));
			catch (TaskCanceledException)
			catch (Exception ex)
				MessageBox.Show(ex.Message, "Sample Error");
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