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 System;
using System.Collections.Generic;
using Esri.ArcGISRuntime.ArcGISServices;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Rasters;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.RasterLayerRasterFunction
{
    [Register("RasterLayerRasterFunction")]
    [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 : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;

        public RasterLayerRasterFunction()
        {
            Title = "ArcGIS raster function (service)";
        }

        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 rasterUri = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/NLCDLandCover2001/ImageServer");

            // Create new image service raster from the URI.
            ImageServiceRaster imageServiceRaster = new ImageServiceRaster(rasterUri);

            try
            {
                // Load the image service raster.
                await imageServiceRaster.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
                const string theJsonString = @"{
                ""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 rasterFunction = RasterFunction.FromJson(theJsonString);

                // NOTE: 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 rasterFunctionArguments = rasterFunction.Arguments;

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

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

                // Create a new raster based on the raster function.
                Raster raster = new Raster(rasterFunction);

                // Create a new raster layer from the raster.
                RasterLayer rasterLayer = new RasterLayer(raster);

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

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

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

                // Zoom the map to the extent of the image service raster (which also the extent of the raster layer).
                await _myMapView.SetViewpointGeometryAsync(arcGISImageServiceInfo.FullExtent);
            }
            catch (Exception e)
            {
                new UIAlertView("Error", e.ToString(), (IUIAlertViewDelegate) null, "OK", null).Show();
            }
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void LoadView()
        {
            // Create the views.
            View = new UIView() { BackgroundColor = ApplicationTheme.BackgroundColor };

            _myMapView = new MapView();
            _myMapView.TranslatesAutoresizingMaskIntoConstraints = false;

            // Add the views.
            View.AddSubviews(_myMapView);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _myMapView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor)
            });
        }
    }
}

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