Raster rendering rule

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Display a raster on a map and apply different rendering rules to that raster.

Image of raster rendering rule

Use case

Raster images whose individual pixels represent elevation values can be rendered in a number of different ways, including representation of slope, aspect, hillshade, and shaded relief. Applying these different rendering rules to the same raster allows for a powerful visual analysis of the data. For example, a geologist could interrogate the raster image to map subtle geological features on a landscape, which may become apparent only through comparing the raster when rendered using several different rules.

How to use the sample

Run the sample and use the drop-down menu at the top to select a rendering rule.

How it works

  1. Create an ImageServiceRaster using a URL to an online image service.
  2. After loading the raster, use imageServiceRaster.ServiceInfo.RenderingRuleInfos to get a list of RenderingRuleInfo supported by the service.
  3. Choose a rendering rule info to apply and use it to create a RenderingRule.
  4. Create a new ImageServiceRaster using the same URL.
  5. Apply the rendering rule to the new raster.
  6. Create a RasterLayer from the raster for display.

Relevant API

  • ImageServiceRaster
  • RasterLayer
  • RenderingRule

About the data

This raster image service contains 9 LAS files covering Charlotte, North Carolina's downtown area. The lidar data was collected in 2007. Four Raster Rules are available for selection: None, RFTAspectColor, RFTHillshade, and RFTShadedReliefElevationColorRamp.

Additional information

Image service rasters of any type can have rendering rules applied to them; they need not necessarily be elevation rasters. See the list of raster function objects and syntax for rendering rules in the ArcGIS REST API documentation.

Tags

raster, rendering rules, visualization

Sample Code

RasterRenderingRule.cs
                                                                                                                                                                                           
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// Copyright 2017 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.

using Android.App;
using Android.OS;
using Android.Views;
using Android.Widget;
using Esri.ArcGISRuntime.ArcGISServices;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Rasters;
using Esri.ArcGISRuntime.UI.Controls;
using System;
using System.Collections.Generic;

namespace ArcGISRuntime.Samples.RasterRenderingRule
{
    [Activity (ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Raster rendering rule",
        category: "Layers",
        description: "Display a raster on a map and apply different rendering rules to that raster.",
        instructions: "Run the sample and use the drop-down menu at the top to select a rendering rule.",
        tags: new[] { "raster", "rendering rules", "visualization" })]
    public class RasterRenderingRule : Activity
    {
        // Hold a reference to the map view
        private MapView _myMapView;

        // Create a empty read-only list for the various rendering rules of the image service raster
        private IReadOnlyList<RenderingRuleInfo> _myReadOnlyListRenderRuleInfos;

        // Create the Uri for the image server
        private Uri _myUri = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/CharlotteLAS/ImageServer");

        // Create a list to store the names of the rendering rule info for the image service raster
        private List<string> _names = new List<string>();

        // Hold a reference to a button for the user to change the rendering rule for the image service raster
        private Button _renderingRulesButton;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            Title = "Raster rendering rule";

            // Create the UI, setup the control references and execute initialization
            CreateLayout();
            Initialize();
        }

        private async void Initialize()
        {
            // Assign a new map to the MapView
            _myMapView.Map = new Map
            {

                // Set the basemap to Streets
                Basemap = new Basemap(BasemapStyle.ArcGISStreets)
            };

            // Create a new image service raster from the Uri
            ImageServiceRaster myImageServiceRaster = new ImageServiceRaster(_myUri);

            try
            {
                // Load the image service raster
                await myImageServiceRaster.LoadAsync();

                // Get the ArcGIS image service info (metadata) from the image service raster
                ArcGISImageServiceInfo myArcGISImageServiceInfo = myImageServiceRaster.ServiceInfo;

                // Get the full extent envelope of the image service raster (the Charlotte, NC area)
                Envelope myEnvelope = myArcGISImageServiceInfo.FullExtent;

                // Define a new view point from the full extent envelope
                Viewpoint myViewPoint = new Viewpoint(myEnvelope);

                // Zoom to the area of the full extent envelope of the image service raster
                await _myMapView.SetViewpointAsync(myViewPoint);

                // Get the rendering rule info (i.e. definitions of how the image should be drawn) info from the image service raster
                _myReadOnlyListRenderRuleInfos = myArcGISImageServiceInfo.RenderingRuleInfos;

                // Loop through each rendering rule info
                foreach (RenderingRuleInfo myRenderingRuleInfo in _myReadOnlyListRenderRuleInfos)
                {
                    // Get the name of the rendering rule info
                    string myRenderingRuleName = myRenderingRuleInfo.Name;

                    // Add the name of the rendering rule info to the list of names
                    _names.Add(myRenderingRuleName);
                }

                // Invoke the button for the user to change the rendering rule of the image service raster
                OnChangeRenderingRuleClicked(_renderingRulesButton, null);
            }
            catch (Exception e)
            {
                new AlertDialog.Builder(this).SetMessage(e.ToString()).SetTitle("Error").Show();
            }
        }

        private void OnChangeRenderingRuleClicked(object sender, EventArgs e)
        {
            // Get the rendering rule button
            Button renderingRuleButton = (Button)sender;

            // Create menu to show the rendering rule options
            PopupMenu renderingRuleMenu = new PopupMenu(this, renderingRuleButton);
            renderingRuleMenu.MenuItemClick += OnChangeRenderingRuleMenuItemClicked;

            // Create menu options
            foreach (string renderingRuleName in _names)
            {
                renderingRuleMenu.Menu.Add(renderingRuleName);
            }

            // Show menu in the view
            renderingRuleMenu.Show();
        }

        private void OnChangeRenderingRuleMenuItemClicked(object sender, PopupMenu.MenuItemClickEventArgs e)
        {
            // Get the rendering rule from the selected item
            string selectedRenderingRuleType = e.Item.TitleCondensedFormatted.ToString();

            // Loop through each rendering rule info in the image service raster
            foreach (RenderingRuleInfo myRenderingRuleInfo in _myReadOnlyListRenderRuleInfos)
            {
                // Get the name of the rendering rule info
                string myRenderingRuleName = myRenderingRuleInfo.Name;

                // If the name of the rendering rule info matches what was chosen by the user, proceed
                if (myRenderingRuleName == selectedRenderingRuleType)
                {
                    // Create a new rendering rule from the rendering rule info
                    RenderingRule myRenderingRule = new RenderingRule(myRenderingRuleInfo);

                    // Create a new image service raster
                    ImageServiceRaster myImageServiceRaster = new ImageServiceRaster(_myUri)
                    {

                        // Set the image service raster's rendering rule to the rendering rule created earlier
                        RenderingRule = myRenderingRule
                    };

                    // Create a new raster layer from the image service raster
                    RasterLayer myRasterLayer = new RasterLayer(myImageServiceRaster);

                    // Add the raster layer to the operational layers of the  map view
                    _myMapView.Map.OperationalLayers.Add(myRasterLayer);
                }
            }
        }

        private void CreateLayout()
        {
            // Create a new vertical layout for the app
            LinearLayout layout = new LinearLayout(this) { Orientation = Orientation.Vertical };

            // Create button to show possible rendering rule options
            _renderingRulesButton = new Button(this)
            {
                Text = "Change Rendering Rule"
            };
            _renderingRulesButton.Click += OnChangeRenderingRuleClicked;

            // Add rendering rule button to the layout
            layout.AddView(_renderingRulesButton);

            // Add the map view to the layout
            _myMapView = new MapView(this);
            layout.AddView(_myMapView);

            // Show the layout in the app
            SetContentView(layout);
        }
    }
}

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