Raster rendering rule

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Sample viewer app

Display a raster on a map and apply different rendering rules to that raster.

screenshot

Use case

Raster images whose individual pixels represent elevation values can be rendered in a number of different ways, including representation of slope, aspect, hillshade, and shaded relief. Applying these different rendering rules to the same raster allows for a powerful visual analysis of the data. For example, a geologist could interrogate the raster image to map subtle geological features on a landscape, which may become apparent only through comparing the raster when rendered using several different rules.

How to use the sample

Run the sample and use the drop-down menu at the top to select a rendering rule.

How it works

  1. Create an ImageServiceRaster using a URL to an online image service.
  2. After loading the raster, use imageServiceRaster::serviceInfo().renderingRuleInfos() to get a list of RenderingRuleInfo supported by the service.
  3. Choose a rendering rule info to apply and use it to create a RenderingRule.
  4. Create a new ImageServiceRaster using the same URL.
  5. Apply the rendering rule to the new raster using imageServiceRaster::setRenderingRule(renderingRuleInfo).
  6. Create a RasterLayer from the raster for display.

Relevant API

  • ImageServiceRaster
  • RasterLayer
  • RenderingRule

About the data

This raster image service contains 9 LAS files covering Charlotte, North Carolina's downtown area. The lidar data was collected in 2007. Four Raster Rules are available for selection: None, RFTAspectColor, RFTHillshade, and RFTShadedReliefElevationColorRamp.

Additional information

Image service rasters of any type can have rendering rules applied to them; they need not necessarily be elevation rasters. See the list of raster function objects and syntax for rendering rules in the ArcGIS REST API documentation.

Tags

raster, rendering rules, visualization

Sample Code

RasterRenderingRule.cppRasterRenderingRule.cppRasterRenderingRule.hRasterRenderingRule.qml
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// [WriteFile Name=RasterRenderingRule, 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 "RasterRenderingRule.h"

#include "Map.h"
#include "MapQuickView.h"
#include "RasterLayer.h"
#include "Basemap.h"
#include "ArcGISTiledLayer.h"
#include "ImageServiceRaster.h"
#include "RenderingRule.h"
#include "RenderingRuleInfo.h"

#include <QJsonObject>
#include <QJsonDocument>

using namespace Esri::ArcGISRuntime;

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

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

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

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

  m_map = new Map(BasemapStyle::ArcGISStreets, this);
  m_mapView->setMap(m_map);

  //! [RasterRenderingRule cpp ImageServiceRaster]
  // set the url
  m_url = QUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/CharlotteLAS/ImageServer");

  // create an image service raster
  m_imageServiceRaster = new ImageServiceRaster(m_url, this);

  // zoom to the raster's extent once it's loaded
  connect(m_imageServiceRaster, &ImageServiceRaster::doneLoading, this, [this]()
  {
    // set the extent of the mapview to the extent defined in the image service raster's service info
    m_mapView->setViewpoint(Viewpoint(m_imageServiceRaster->serviceInfo().fullExtent()));

    // get the rendering rule infos
    const QList<RenderingRuleInfo> renderingRuleInfos = m_imageServiceRaster->serviceInfo().renderingRuleInfos();
    if (renderingRuleInfos.length() > 0)
    {
      for (const RenderingRuleInfo& renderingRuleInfo : renderingRuleInfos)
      {
        // populate the list with the rendering rule names
        m_renderingRuleNames << renderingRuleInfo.name();
      }
      emit renderingRuleNamesChanged();
    }
  });
  //! [RasterRenderingRule cpp ImageServiceRaster]

  // 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 RasterRenderingRule::applyRenderingRule(int index)
{
  //! [ImageServiceRaster Create a rendering rule]
  // get the rendering rule info from the service info
  RenderingRuleInfo renderingRuleInfo = m_imageServiceRaster->serviceInfo().renderingRuleInfos().at(index);
  // create a new rendering rule with the rendering rule info
  RenderingRule* renderingRule = new RenderingRule(renderingRuleInfo, this);
  // create an image service raster
  ImageServiceRaster* isr = new ImageServiceRaster(m_url, this);
  // set the rendering rule
  isr->setRenderingRule(renderingRule);
  //! [ImageServiceRaster Create a rendering rule]
  // create a new raster layer using the image service raster
  RasterLayer* rasterLayer = new RasterLayer(isr, this);
  // add the raster layer to the map
  m_map->operationalLayers()->append(rasterLayer);
}

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