Raster function service

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

Image of raster function 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 arguments of the raster function with rasterFunction.arguments.
  4. Get the names of the raster arguments with rasterFunctionArguments.rasterNames.
  5. Set the raster argument with rasterFunction.setRaster(rasterName, raster).
  6. Create a new Raster referring to the raster function.
  7. Create a RasterLayer to visualize the computed raster.
  8. Add the raster layer to the map.

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

MainActivity.kt
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/*
 * Copyright 2020 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.arcgisruntime.sample.rasterfunctionservice

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
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.sample.rasterfunctionservice.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

  private val activityMainBinding by lazy {
    ActivityMainBinding.inflate(layoutInflater)
  }

  private val mapView: MapView by lazy {
    activityMainBinding.mapView
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(activityMainBinding.root)

    // authentication with an API key or named user is required to access basemaps and other
    // location services
    ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY)

    // create a Dark Gray Vector BaseMap
    val map = ArcGISMap(BasemapStyle.ARCGIS_DARK_GRAY)
    // set the map to be displayed in this view
    mapView.map = map
    // create image service raster as raster layer
    val imageServiceRaster = ImageServiceRaster(
      resources.getString(R.string.image_service_raster_url)
    )
    val imageRasterLayer = RasterLayer(imageServiceRaster)
    map.operationalLayers.add(imageRasterLayer)
    // zoom to the extent of the raster service
    imageRasterLayer.addDoneLoadingListener {
      if (imageRasterLayer.loadStatus == LoadStatus.LOADED) {
        // zoom to extent of raster
        val centerPnt = imageServiceRaster.serviceInfo.fullExtent.center
        mapView.setViewpointCenterAsync(centerPnt, 55000000.0)
        // update raster with simplified hillshade
        applyRasterFunction(imageServiceRaster)
      }
    }
  }

  /**
   * Apply a raster function on the given Raster
   *
   * @param raster Input raster to apply function
   */
  private fun applyRasterFunction(raster: Raster) {
    // create raster function from json string
    val rasterFunction = RasterFunction.fromJson(resources.getString(R.string.hillshade_simplified))
    // get parameter name value pairs used by hillshade
    val rasterFunctionArguments = rasterFunction.arguments
    // get list of raster names associated with raster function
    val rasterName = rasterFunctionArguments.rasterNames
    // set raster to the raster name
    rasterFunctionArguments.setRaster(rasterName[0], raster)
    // create raster as raster layer
    val raster = Raster(rasterFunction)
    val hillshadeLayer = RasterLayer(raster)
    // add hillshade raster
    mapView.map.operationalLayers.add(hillshadeLayer)
  }

  override fun onPause() {
    super.onPause()
    mapView.pause()
  }

  override fun onResume() {
    super.onResume()
    mapView.resume()
  }

  override fun onDestroy() {
    super.onDestroy()
    mapView.dispose()
  }
}

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