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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 Raster
from a raster file.
Create a RasterLayer
from 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 .
About the data
The raster used in this sample shows an area in the south of the Shasta-Trinity National Forest, California.
colormap, data, raster, renderer, visualization
Sample CodeRasterColormapRenderer.cpp RasterColormapRenderer.cpp RasterColormapRenderer.h RasterColormapRenderer.qml
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// [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
# include "RasterColormapRenderer.h"
# include "ColormapRenderer.h"
# include "Map.h"
# include "MapQuickView.h"
# include "Raster.h"
# include "RasterLayer.h"
# include "Error.h"
# include "MapTypes.h"
# include "MapViewTypes.h"
# include "TaskWatcher.h"
# include "LayerListModel.h"
# include "Envelope.h"
# include <QtCore/qglobal.h>
# include <QStandardPaths>
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-> setViewpointGeometry (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;
}