Raster function (service)

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

screenshot

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. Set the raster argument with rasterFunction::setRaster(rasterName, imageServiceRaster).
  4. Create a new Raster referring to the raster function.
  5. Create a RasterLayer to visualize the computed raster.
  6. 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

RasterFunctionService.cppRasterFunctionService.cppRasterFunctionService.hRasterFunctionService.qml
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// [WriteFile Name=RasterFunctionService, Category=Layers]
// [Legal]
// 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.
// [Legal]

#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD

#include "RasterFunctionService.h"

#include "Map.h"
#include "MapQuickView.h"
#include "RasterLayer.h"
#include "Basemap.h"
#include "ImageServiceRaster.h"
#include "RasterFunction.h"

#include <QDir>
#include <QtCore/qglobal.h>

#ifdef Q_OS_IOS
#include <QStandardPaths>
#endif // Q_OS_IOS

using namespace Esri::ArcGISRuntime;

// helper method to get cross platform data path
namespace
{
  QString defaultDataPath()
  {
    QString dataPath;

  #ifdef Q_OS_ANDROID
    dataPath = "/sdcard";
  #elif defined Q_OS_IOS
    dataPath = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
  #else
    dataPath = QDir::homePath();
  #endif

    return dataPath;
  }
} // namespace

RasterFunctionService::RasterFunctionService(QQuickItem* parent /* = nullptr */):
  QQuickItem(parent)
{
}

void RasterFunctionService::init()
{
  // Register the map view for QML
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<RasterFunctionService>("Esri.Samples", 1, 0, "RasterFunctionServiceSample");
}

void RasterFunctionService::componentComplete()
{
  QQuickItem::componentComplete();

  m_dataPath = defaultDataPath() + "/ArcGIS/Runtime/Data/raster";

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");
  m_mapView->setWrapAroundMode(WrapAroundMode::Disabled);

  // create a new tiled layer to add a basemap
  m_map = new Map(BasemapStyle::ArcGISStreets, this);
  m_mapView->setMap(m_map);

  // create an image service raster
  m_imageServiceRaster = new ImageServiceRaster(QUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/NLCDLandCover2001/ImageServer"), this);
  // zoom to the raster's extent once it's loaded
  connect(m_imageServiceRaster, &ImageServiceRaster::doneLoading, this, [this]()
  {
    constexpr double scale = 50000000.;
    Viewpoint vpCenter = Viewpoint(m_imageServiceRaster->serviceInfo().fullExtent().center(), scale);
    m_mapView->setViewpoint(vpCenter);
  });

  // create a raster layer using the image service raster
  m_rasterLayer = new RasterLayer(m_imageServiceRaster, this);
  // add the raster layer to the map's operational layers
  m_map->operationalLayers()->append(m_rasterLayer);
}

void RasterFunctionService::applyRasterFunction()
{
  if (!QFile::exists(m_dataPath + "/hillshade_simplified.json"))
  {
    qDebug() << "JSON file for the raster function does not exist.";
    return;
  }

  //! [ImageServiceRaster Apply a raster function]
  RasterFunction* rasterFunction = new RasterFunction(m_dataPath + "/hillshade_simplified.json", this);
  RasterFunctionArguments* arguments = rasterFunction->arguments();
  arguments->setRaster("raster", m_imageServiceRaster);

  // create a new raster with the raster function and add to the operational layer
  Raster* raster = new Raster(rasterFunction, this);
  RasterLayer* rasterLayer = new RasterLayer(raster, this);
  //! [ImageServiceRaster Apply a raster function]

  m_map->operationalLayers()->clear();
  //! [ImageServiceRaster cpp add raster operational]
  m_map->operationalLayers()->append(rasterLayer);
  //! [ImageServiceRaster cpp add raster operational]
}

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