Apply raster function to raster from service

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Load a raster from a service, then apply a function to it.

Image of apply raster function to raster from service

Use case

Raster functions allow processing operations that can be applied to one or more rasters on the fly. Functions can be applied to rasters that come from a service. A land survey agency may apply hillshade and aspect functions to rasters with elevation data in order to better determine the topography of a landscape and to make further planning decisions.

How to use the sample

The raster function is applied automatically when the sample starts and the result is displayed.

How it works

  1. Create the ImageServiceRaster referring to the image server URL.
  2. Create the RasterFunction from a JSON string.
  3. Get the name of the raster argument to the function with rasterFunction.Arguments.GetRasterNames().First()
  4. Set the raster argument with rasterFunction.SetRaster(rasterName, imageServiceRaster).
  5. Create a new Raster referring to the raster function.
  6. Create a RasterLayer to visualize the computed raster.
  7. Display the raster.

Relevant API

  • ImageServiceRaster
  • Raster
  • RasterFunction
  • RasterFunctionArguments
  • RasterLayer

About the data

The sample applies a hillshade function to a raster produced from the National Land Cover Database, NLCDLandCover2001. You can learn more about the hillshade function in the ArcMap documentation.

Additional information

The raster function computation happens locally on the client device.

Tags

function, layer, raster, raster function, service

Sample Code

RasterLayerRasterFunction.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.Widget;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Rasters;
using Esri.ArcGISRuntime.ArcGISServices;
using Esri.ArcGISRuntime.UI.Controls;
using System;
using System.Collections.Generic;

namespace ArcGISRuntime.Samples.RasterLayerRasterFunction
{
    [Activity (ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Apply raster function to raster from service",
        category: "Layers",
        description: "Load a raster from a service, then apply a function to it.",
        instructions: "The raster function is applied automatically when the sample starts and the result is displayed.",
        tags: new[] { "function", "layer", "raster", "raster function", "service" })]
    public class RasterLayerRasterFunction : Activity
    {
        // Hold a reference to the map view
        private MapView _myMapView;

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

            Title = "ArcGIS raster function (service)";

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

        private async void Initialize()
        {
            // Create new map with the streets basemap
            Map myMap = new Map(BasemapStyle.ArcGISStreets);

            // Create a Uri to the image service raster
            Uri myUri = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/NLCDLandCover2001/ImageServer");

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

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

                // NOTE: This is the ASCII text for actual raw JSON string:
                // ========================================================
                //{
                //  "raster_function_arguments":
                //  {
                //    "z_factor":{"double":25.0,"type":"Raster_function_variable"},
                //    "slope_type":{"raster_slope_type":"none","type":"Raster_function_variable"},
                //    "azimuth":{"double":315,"type":"Raster_function_variable"},
                //    "altitude":{"double":45,"type":"Raster_function_variable"},
                //    "type":"Raster_function_arguments",
                //    "raster":{"name":"raster","is_raster":true,"type":"Raster_function_variable"},
                //    "nbits":{"int":8,"type":"Raster_function_variable"}
                //  },
                //  "raster_function":{"type":"Hillshade_function"},
                //  "type":"Raster_function_template"
                //}

                // Define the JSON string needed for the raster function
                string theJSON_String =
                    @"{
                ""raster_function_arguments"":
                {
                  ""z_factor"":{ ""double"":25.0,""type"":""Raster_function_variable""},
                  ""slope_type"":{ ""raster_slope_type"":""none"",""type"":""Raster_function_variable""},
                  ""azimuth"":{ ""double"":315,""type"":""Raster_function_variable""},
                  ""altitude"":{ ""double"":45,""type"":""Raster_function_variable""},
                  ""type"":""Raster_function_arguments"",
                  ""raster"":{ ""name"":""raster"",""is_raster"":true,""type"":""Raster_function_variable""},
                  ""nbits"":{ ""int"":8,""type"":""Raster_function_variable""}
                },
              ""raster_function"":{ ""type"":""Hillshade_function""},
              ""type"":""Raster_function_template""
            }";

                // Create a raster function from the JSON string using the static/Shared method called: RasterFunction.FromJson(json as String)
                RasterFunction myRasterFunction = RasterFunction.FromJson(theJSON_String);

                // NOTE: Depending on your platform/device, you could have alternatively created the raster function via a JSON string that is contained in a
                // file on disk (ex: hillshade_simplified.json) via the constructor: Esri.ArcGISRuntime.Rasters.RasterFunction(path as String)

                // Get the raster function arguments
                RasterFunctionArguments myRasterFunctionArguments = myRasterFunction.Arguments;

                // Get the list of names from the raster function arguments
                IReadOnlyList<string> myRasterNames = myRasterFunctionArguments.GetRasterNames();

                // Apply the first raster name and image service raster in the raster function arguments
                myRasterFunctionArguments.SetRaster(myRasterNames[0], myImageServiceRaster);

                // Create a new raster based on the raster function
                Raster myRaster = new Raster(myRasterFunction);

                // Create a new raster layer from the raster
                RasterLayer myRasterLayer = new RasterLayer(myRaster);

                // Add the raster layer to the maps layer collection
                myMap.OperationalLayers.Add(myRasterLayer);

                // Assign the map to the map view
                _myMapView.Map = myMap;

                // Get the service information (aka. metadata) about the image service raster
                ArcGISImageServiceInfo myArcGISImageServiceInfo = myImageServiceRaster.ServiceInfo;

                // Zoom the map to the extent of the image service raster (which also the extent of the raster layer)
                await _myMapView.SetViewpointGeometryAsync(myArcGISImageServiceInfo.FullExtent);

                // NOTE: The sample zooms to the extent of the ImageServiceRaster. Currently the ArcGIS Runtime does not
                // support zooming a RasterLayer out beyond 4 times it's published level of detail. The sample uses
                // MapView.SetViewpointCenterAsync() method to ensure the image shows when the app starts. You can see
                // the effect of the image service not showing when you zoom out to the full extent of the image and beyond.
            }
            catch (Exception e)
            {
                new AlertDialog.Builder(this).SetMessage(e.ToString()).SetTitle("Error").Show();
            }
        }

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

            // 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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