Raster function

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

Image of raster function

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

Pan and zoom to explore the raster function applied to the raster layer.

How it works

  1. Create the ImageServiceRaster referring to the image server URL.
  2. Create the RasterFunction from a JSON string.
  3. Get the arguments of the raster function with rasterFunction.getArguments().
  4. Get the names of the raster arguments with rasterFunctionArguments.getRasterNames().
  5. Set the raster argument with rasterFunction.setRaster(rasterName, imageServiceRaster).
  6. Create a new Raster referring to the raster function.
  7. Create a RasterLayer to visualize the computed raster.
  8. 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

RasterFunctionSample.java
                                                                                                                                              
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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.
 */

package com.esri.samples.raster_function;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.layers.RasterLayer;
import com.esri.arcgisruntime.loadable.LoadStatus;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.view.MapView;
import com.esri.arcgisruntime.raster.ImageServiceRaster;
import com.esri.arcgisruntime.raster.Raster;
import com.esri.arcgisruntime.raster.RasterFunction;
import com.esri.arcgisruntime.raster.RasterFunctionArguments;

public class RasterFunctionSample extends Application {

  private ImageServiceRaster imageServiceRaster; // keep loadables in scope to avoid garbage collection
  private MapView mapView;

  @Override
  public void start(Stage stage) {

    try {
      // create stack pane and application scene
      StackPane stackPane = new StackPane();
      Scene scene = new Scene(stackPane);

      // set title, size, and add scene to stage
      stage.setTitle("Raster Function Sample");
      stage.setWidth(800);
      stage.setHeight(700);
      stage.setScene(scene);
      stage.show();

      // authentication with an API key or named user is required to access basemaps and other location services
      String yourAPIKey = System.getProperty("apiKey");
      ArcGISRuntimeEnvironment.setApiKey(yourAPIKey);

      // create a map with the dark gray basemap style
      ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_DARK_GRAY);

      // create a map view and set the map to it
      mapView = new MapView();
      mapView.setMap(map);

      // create an image service raster from an online raster service
      imageServiceRaster = new ImageServiceRaster("https://sampleserver6.arcgisonline" +
          ".com/arcgis/rest/services/NLCDLandCover2001/ImageServer");
      imageServiceRaster.loadAsync();
      imageServiceRaster.addDoneLoadingListener(() -> {

          if (imageServiceRaster.getLoadStatus() == LoadStatus.LOADED) {
            // create raster function from local json file
            File jsonFile = new File(System.getProperty("data.dir"), "./samples-data/raster/hillshade_simplified.json");
            try (Scanner scanner = new Scanner(jsonFile)) {
              // read in the complete file as a string
              String json = scanner.useDelimiter("\\A").next();
              RasterFunction rasterFunction = RasterFunction.fromJson(json);
              RasterFunctionArguments arguments = rasterFunction.getArguments();
              // apply the raster function
              arguments.setRaster(arguments.getRasterNames().get(0), imageServiceRaster);
              // create a new raster from the function definition
              Raster raster = new Raster(rasterFunction);
              // create raster layer and add to map as operational layer
              RasterLayer hillshadeLayer = new RasterLayer(raster);
              // add the hillshade raster layer to the map
              map.getOperationalLayers().add(hillshadeLayer);
              hillshadeLayer.addDoneLoadingListener(() -> {
                if (hillshadeLayer.getLoadStatus() == LoadStatus.LOADED) {
                  // set viewpoint on the raster
                  mapView.setViewpointGeometryAsync(hillshadeLayer.getFullExtent(), 150);
                } else {
                  Alert alert = new Alert(Alert.AlertType.ERROR, "Failed to load the hillshade raster layer");
                  alert.show();
                }
              });
            } catch (FileNotFoundException e) {
              Alert alert = new Alert(Alert.AlertType.ERROR, "Failed to locate raster function json");
              alert.show();
            }
          } else {
            Alert alert = new Alert(Alert.AlertType.ERROR, "Failed to load image service raster");
            alert.show();
          }

      });

      // add the map view to stack pane
      stackPane.getChildren().addAll(mapView);
    } catch (Exception e) {
      // on any error, display the stack trace.
      e.printStackTrace();
    }
  }

  /**
   * Stops and releases all resources used in application.
   */
  @Override
  public void stop() {

    if (mapView != null) {
      mapView.dispose();
    }
  }

  /**
   * Opens and runs application.
   *
   * @param args arguments passed to this application
   */
  public static void main(String[] args) {

    Application.launch(args);
  }

}

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