Apply a colormap renderer to a raster.
      
   
    
Use case
A colormap renderer transforms pixel values in a raster to display raster data based on specific colors, aiding in visual analysis of the data. For example, a forestry commission may want to quickly visualize areas above and below the tree-line line occurring at a know elevation on a raster containing elevation values. They could overlay a transparent colormap set to color those areas below the tree-line elevation green, and those above white.
How to use the sample
Pan and zoom to explore the effect of the colormap applied to the raster.
How it works
- Create a Rasterfrom a raster file.
- Create a RasterLayerfrom the raster.
- Create a QList<QColor>: colors at the beginning of the list replace the darkest values in the raster and colors at the end of the list replaced the brightest values of the raster.
- Create a colormap renderer with the color list and apply it to the raster layer with RasterLayer::setRenderer(RasterRenderer *renderer).
Relevant API
- ColormapRenderer
- Raster
- RasterLayer
Offline Data
Read more about how to set up the sample's offline data here.
| Link | Local Location | 
|---|---|
| ShastaBW.tif raster | <userhome>/ArcGIS/Runtime/Data/raster/ShastaBW.tif | 
About the data
The raster used in this sample shows an area in the south of the Shasta-Trinity National Forest, California.
Tags
colormap, data, raster, renderer, visualization
Sample Code
// [WriteFile Name=RasterColormapRenderer, 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
// sample headers
#include "RasterColormapRenderer.h"
// ArcGIS Maps SDK headers
#include "ColormapRenderer.h"
#include "Envelope.h"
#include "Error.h"
#include "LayerListModel.h"
#include "Map.h"
#include "MapQuickView.h"
#include "MapTypes.h"
#include "MapViewTypes.h"
#include "Raster.h"
#include "RasterLayer.h"
// Qt headers
#include <QFuture>
#include <QStandardPaths>
#include <QtCore/qglobal.h>
using namespace Esri::ArcGISRuntime;
// helper method to get cross platform data path
namespace
{
QString defaultDataPath()
{
  QString dataPath;
#ifdef Q_OS_IOS
  dataPath = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
#else
  dataPath = QStandardPaths::writableLocation(QStandardPaths::HomeLocation);
#endif
  return dataPath;
}
} // namespace
RasterColormapRenderer::RasterColormapRenderer(QQuickItem* parent /* = nullptr */):
  QQuickItem(parent),
  m_dataPath(defaultDataPath() + "/ArcGIS/Runtime/Data/raster")
{
}
RasterColormapRenderer::~RasterColormapRenderer() = default;
void RasterColormapRenderer::init()
{
  // Register the map view for QML
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<RasterColormapRenderer>("Esri.Samples", 1, 0, "RasterColormapRendererSample");
}
void RasterColormapRenderer::componentComplete()
{
  QQuickItem::componentComplete();
  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");
  m_mapView->setWrapAroundMode(WrapAroundMode::Disabled);
  //! [RasterColormapRenderer cpp add raster basemap]
  // Create the raster and raster layer
  Raster* raster = new Raster(m_dataPath + "/ShastaBW.tif", this);
  m_rasterLayer = new RasterLayer(raster, this);
  connect(m_rasterLayer, &RasterLayer::doneLoading, this, [this](const Error& error)
  {
    if (!error.isEmpty())
    {
      qDebug() << error.message() << error.additionalMessage();
      return;
    }
    m_mapView->setViewpointGeometryAsync(m_rasterLayer->fullExtent(), 50);
  });
  ColormapRenderer* colormapRenderer = createRenderer();
  // set the colormap renderer on the raster layer
  m_rasterLayer->setRenderer(colormapRenderer);
  // Add the raster to the map as an operational layer
  Map* map = new Map(BasemapStyle::ArcGISImageryStandard, this);
  map->operationalLayers()->append(m_rasterLayer);
  m_mapView->setMap(map);
  //! [RasterColormapRenderer cpp add raster basemap]
}
ColormapRenderer *RasterColormapRenderer::createRenderer()
{
  // create a color map where values 0-150 are red and 150-250 are yellow
  QList<QColor> colors;
  colors.reserve(250);
  for (int i = 0; i < 250; ++i)
    colors.append( i < 150 ? Qt::red : Qt::yellow);
  // create a colormap renderer
  ColormapRenderer* colormapRenderer = new ColormapRenderer(colors, this);
  return colormapRenderer;
}