Raster function (file)

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Apply a raster function to a local raster file and display the output with a raster layer.

screenshot

Use case

Raster functions allow processing operations that can be applied to one or more rasters on the fly. 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

Load the sample to see a raster function applied to a raster.

How it works

  1. Create a RasterFunction using the path to a local raster function JSON file.
  2. Set the raster function arguments as required by the function used.
  3. Use the raster function to create a new Raster.
  4. Set the raster to a RasterLayer and display it in the Map.

Relevant API

  • Raster
  • RasterFunction
  • RasterLayer

Offline Data

Read more about how to set up the sample's offline data here.

Link Local Location
Shasta.tif raster <userhome>/ArcGIS/Runtime/Data/raster/Shasta_Elevation.tif
color.json raster function <userhome>/ArcGIS/Runtime/Data/raster/color.json

About the data

The raster function in the provided JSON file blends a color image with a greyscale image (in this case, a raster image containing elevation data), to add a hillshade effect to the input raster.

Additional information

Learn more about raster functions in the ArcGIS Pro documentation.

Tags

analysis, function, image, layer, processing, raster, raster function, transformation

Sample Code

RasterFunctionFile.cppRasterFunctionFile.cppRasterFunctionFile.hRasterFunctionFile.qml
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// [WriteFile Name=RasterFunctionFile, 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 "RasterFunctionFile.h"

#include "Map.h"
#include "MapQuickView.h"
#include "Basemap.h"
#include "Raster.h"
#include "RasterLayer.h"
#include "RasterFunction.h"
#include "Envelope.h"

#include <QDir>
#include <QFileInfo>
#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

RasterFunctionFile::RasterFunctionFile(QQuickItem* parent /* = nullptr */):
  QQuickItem(parent),
  m_dataPath(defaultDataPath() + "/ArcGIS/Runtime/Data/raster/")
{
}

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

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

  // get data path
  m_rasterPath = m_dataPath + "Shasta_Elevation.tif";

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");

  // Create a map using the imagery basemap
  m_map = new Map(BasemapStyle::ArcGISImageryStandard, this);

  // Add the Raster Layer
  m_raster = new Raster(m_rasterPath, this);
  RasterLayer* rasterLayer = new RasterLayer(m_raster, this);
  rasterLayer->setOpacity(0.5);

  connect(rasterLayer, &RasterLayer::doneLoading, this, &RasterFunctionFile::readyChanged);

  m_map->operationalLayers()->append(rasterLayer);

  // Set initial Extent
  Envelope env = Envelope::fromJson("{\"spatialReference\": {\"latestWkid\": 3857, \"wkid\": 102100 },\"xmax\": -13591503.517810356,\"xmin\": -13606233.44023646,\"ymax\": 4982810.138527592,\"ymin\": 4971762.696708013}");
  m_map->setInitialViewpoint(Viewpoint(env));

  // Set map to map view
  m_mapView->setMap(m_map);
}

void RasterFunctionFile::applyRasterFunction()
{
  // create raster function
  RasterFunction* rasterFunction = createRasterFunction();

  // check for valid raster function
  if (!rasterFunction)
    return;

  // create the raster from the raster function
  Raster* raster = new Raster(rasterFunction, this);

  // create raster layer from raster
  RasterLayer* rasterLayer = new RasterLayer(raster, this);
  rasterLayer->setOpacity(0.5);

  // add raster to map
  m_map->operationalLayers()->clear();
  m_map->operationalLayers()->append(rasterLayer);
}

RasterFunction* RasterFunctionFile::createRasterFunction()
{
  // Check if the raster function json exists
  QFileInfo colorJson(m_dataPath + "/color.json");
  if (!colorJson.exists())
    return nullptr;

  // create a RasterFunction
  RasterFunction* rasterFunction = new RasterFunction(m_dataPath + "/color.json", this);

  // check for valid raster function
  if (!rasterFunction)
    return nullptr;

  // set the number of rasters required - 2 in this case
  rasterFunction->arguments()->setRaster("raster", m_raster);
  rasterFunction->arguments()->setRaster("raster", m_raster);

  return rasterFunction;
}

bool RasterFunctionFile::ready() const
{
  return m_raster && m_raster->loadStatus() == LoadStatus::Loaded;
}

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