Stretch renderer

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Sample viewer app

Use a stretch renderer to enhance the visual contrast of raster data for analysis.

screenshot

Use case

An appropriate stretch renderer can enhance the contrast of raster imagery, allowing the user to control how their data is displayed for efficient imagery analysis.

How to use the sample

Click 'Edit Renderer' to open the stretch renderer options. Choose one of the stretch parameter types:

  • Standard deviation - a linear stretch defined by the standard deviation of the pixel values
  • Min-max - a linear stretch based on minimum and maximum pixel values
  • Percent clip - a linear stretch between the defined percent clip minimum and percent clip maximum pixel values

Then configure the parameters and click 'Render'.

How it works

  1. Create a Raster from a raster file.
  2. Create a RasterLayer from the Raster.
  3. Add the layer to the map.
  4. Create a StretchRenderer, specifying the stretch parameters and other properties.
  5. Set the Renderer on the RasterLayer with rasterLayer::setRenderer(renderer).

Relevant API

  • ColorRamp
  • MinMaxStretchParameters
  • PercentClipStretchParameters
  • Raster
  • RasterLayer
  • StandardDeviationStretchParameters
  • StretchParameters
  • StretchRenderer

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.tif

About the data

This sample uses a raster imagery tile of an area of forested mountainous terrain and rivers.

Additional information

See Stretch function in the ArcMap documentation for more information about the types of stretches that can be performed.

Tags

analysis, deviation, histogram, imagery, interpretation, min-max, percent clip, pixel, raster, stretch, symbology, visualization

Sample Code

RasterStretchRenderer.cppRasterStretchRenderer.cppRasterStretchRenderer.hInputWithLabel.qmlRasterStretchRenderer.qml
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// [WriteFile Name=RasterStretchRenderer, 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 "RasterStretchRenderer.h"

#include "Map.h"
#include "MapQuickView.h"
#include "MinMaxStretchParameters.h"
#include "PercentClipStretchParameters.h"
#include "Raster.h"
#include "RasterLayer.h"
#include "StretchRenderer.h"
#include "StandardDeviationStretchParameters.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

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

RasterStretchRenderer::~RasterStretchRenderer() = default;

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

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

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

  // Create the raster and raster layer
  Raster* raster = new Raster(m_dataPath + "/Shasta.tif", this);
  m_rasterLayer = new RasterLayer(raster, this);

  // Add the raster to the map
  Basemap* basemap = new Basemap(m_rasterLayer, this);
  Map* map = new Map(basemap, this);
  m_mapView->setMap(map);
}

//! [RasterStretchRenderer cpp set renderers]
void RasterStretchRenderer::applyMinMax(double min, double max)
{
  MinMaxStretchParameters stretchParams(QList<double>{min}, QList<double>{max});
  QList<double> gammas;
  bool estimateStats = true;
  StretchRenderer* renderer = new StretchRenderer(stretchParams, gammas, estimateStats, PresetColorRampType::None, this);

  m_rasterLayer->setRenderer(renderer);
}

void RasterStretchRenderer::applyPercentClip(double min, double max)
{
  PercentClipStretchParameters stretchParams(min, max);
  QList<double> gammas;
  bool estimateStats = true;
  StretchRenderer* renderer = new StretchRenderer(stretchParams, gammas, estimateStats, PresetColorRampType::None, this);

  m_rasterLayer->setRenderer(renderer);
}

void RasterStretchRenderer::applyStandardDeviation(double factor)
{
  StandardDeviationStretchParameters stretchParams(factor);
  QList<double> gammas;
  bool estimateStats = true;
  StretchRenderer* renderer = new StretchRenderer(stretchParams, gammas, estimateStats, PresetColorRampType::None, this);

  m_rasterLayer->setRenderer(renderer);
}
//! [RasterStretchRenderer cpp set renderers]

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