Densify and generalize | ArcGIS Maps SDK for Qt

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A multipart geometry can be densified by adding interpolated points at regular intervals. Generalizing a multipart geometry simplifies it while preserving its general shape. Densifying a multipart geometry adds more vertices at regular intervals.

Use case

The sample shows a polyline representing a ship’s location at irregular intervals. The density of vertices along the ship’s route is appropriate to represent the path of the ship at the sample map view’s initial scale. However, that level of detail may be too great if you wanted to show a polyline of the ship’s movement down the whole of the Willamette river. Then, you might consider generalizing the polyline to still faithfully represent the ship’s passage on the river without having an overly complicated geometry.

Densifying a multipart geometry can be used to more accurately represent curved lines or to add more regularity to the vertices making up a multipart geometry.

How to use the sample

Use the sliders to control the parameters of the densify and generalize methods. You can deselect the checkboxes for either method to remove its effect from the result polyline.

How it works

Use the static method GeometryEngine::densify(polyline, maxSegmentLength) to densify the polyline object. The resulting polyline object will have more points along the line, so that there are no points greater than maxSegmentLength from the next point.
Use the static method GeometryEngine::generalize(polyline, maxDeviation, true) to generalize the polyline object. The resulting polyline object will have points shifted from the original line to simplify the shape. None of these points can deviate farther from the original line than maxDeviation. The last parameter, removeDegenerateParts, will clean up extraneous parts of a multipart geometry. This will have no effect in this sample as the polyline does not contain extraneous parts.
Note that maxSegmentLength and maxDeviation are in the units of the geometry’s coordinate system. In this example, a cartesian coordinate system is used and at a small enough scale that geodesic distances are not required.

Relevant API

GeometryEngine
Multipoint
Point
PointCollection
Polyline
SimpleLineSymbol
SpatialReference

Sample Code

DensifyAndGeneralize.cpp

DensifyAndGeneralize.h

DensifyAndGeneralize.qml

main.cpp

// [WriteFile Name=DensifyAndGeneralize, Category=Geometry]
// [Legal]
// Copyright 2018 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 "DensifyAndGeneralize.h"

// ArcGIS Maps SDK headers
#include "Envelope.h"
#include "GeometryEngine.h"
#include "Graphic.h"
#include "GraphicListModel.h"
#include "GraphicsOverlay.h"
#include "GraphicsOverlayListModel.h"
#include "ImmutablePart.h"
#include "ImmutablePartCollection.h"
#include "ImmutablePointCollection.h"
#include "Map.h"
#include "MapQuickView.h"
#include "MapTypes.h"
#include "MultipointBuilder.h"
#include "Point.h"
#include "PointCollection.h"
#include "Polyline.h"
#include "PolylineBuilder.h"
#include "SimpleLineSymbol.h"
#include "SimpleMarkerSymbol.h"
#include "SpatialReference.h"
#include "SymbolTypes.h"

// Qt headers
#include <QFuture>

using namespace Esri::ArcGISRuntime;

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

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

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

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

  // Create a map using the streets night vector basemap
  m_map = new Map(BasemapStyle::ArcGISStreetsNight, this);

  // Add a GraphicsOverlay
  m_graphicsOverlay = new GraphicsOverlay(this);
  m_mapView->graphicsOverlays()->append(m_graphicsOverlay);

  // Get Points along the river
  PointCollection* pointCollection = createPointCollection();

  // original multipart red graphic
  MultipointBuilder multipointBuilder(pointCollection->spatialReference());
  multipointBuilder.setPoints(pointCollection);
  SimpleMarkerSymbol* originalSms = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("red"), 7.0f /*size*/, this);
  m_originalMultipointGraphic = new Graphic(multipointBuilder.toGeometry(), originalSms, this);
  m_originalMultipointGraphic->setZIndex(0);
  m_graphicsOverlay->graphics()->append(m_originalMultipointGraphic);

  // original red dotted line graphic
  PolylineBuilder polylineBuilder(pointCollection->spatialReference());
  const int pointCollectionSize = pointCollection->size();
  for (int i = 0; i < pointCollectionSize; i++)
  {
    polylineBuilder.addPoint(pointCollection->point(i));
  }
  SimpleLineSymbol* originalSls = new SimpleLineSymbol(SimpleLineSymbolStyle::Dot, QColor("red"), 3.0f /*size*/, this);
  m_originalLineGraphic = new Graphic(polylineBuilder.toGeometry(), originalSls, this);
  m_originalLineGraphic->setZIndex(1);
  m_graphicsOverlay->graphics()->append(m_originalLineGraphic);

  // resulting (densified and generalized) multipart magenta graphic
  SimpleMarkerSymbol* resultSms = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("magenta"), 7.0f /*size*/, this);
  m_resultMultipointGraphic = new Graphic(this);
  m_resultMultipointGraphic->setSymbol(resultSms);
  m_resultMultipointGraphic->setZIndex(2);
  m_graphicsOverlay->graphics()->append(m_resultMultipointGraphic);

  // resulting (densified and generalized) multipart magenta graphic
  SimpleLineSymbol* resultSls = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("magenta"), 3.0f /*size*/, this);
  m_resultLineGraphic = new Graphic(this);
  m_resultLineGraphic->setSymbol(resultSls);
  m_resultLineGraphic->setZIndex(3);
  m_graphicsOverlay->graphics()->append(m_resultLineGraphic);

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

  // set viewpoint
  m_mapView->setViewpointGeometryAsync(m_originalMultipointGraphic->geometry().extent(), 100);
}

void DensifyAndGeneralize::updateGeometry(bool densify, double maxSegmentLength, bool generalize, double maxDeviation)
{
  if (!m_originalLineGraphic)
    return;

  // Get the initial Geometry
  Polyline polyline = geometry_cast<Polyline>(m_originalLineGraphic->geometry());
  if (polyline.isEmpty())
    return;

  // Generalize the polyline
  if (generalize)
    polyline = geometry_cast<Polyline>(GeometryEngine::generalize(polyline, maxDeviation, true));

  // Densify the polyline
  if (densify)
    polyline = geometry_cast<Polyline>(GeometryEngine::densify(polyline, maxSegmentLength));

  // Update the line graphic
  m_resultLineGraphic->setGeometry(polyline);

  // Update the multipoint graphic
  if (polyline.parts().size() < 1)
    return;

  MultipointBuilder multipointBuilder(polyline.spatialReference());
  PointCollection* pointCollection = new PointCollection(polyline.spatialReference(), this);

  ImmutablePointCollection polylinePoints = polyline.parts().part(0).points();
  const int polylinePointsSize = polylinePoints.size();
  for (int i = 0; i < polylinePointsSize; i++)
  {
    pointCollection->addPoint(polylinePoints.point(i));
  }
  multipointBuilder.setPoints(pointCollection);
  m_resultMultipointGraphic->setGeometry(multipointBuilder.toGeometry());
}

PointCollection* DensifyAndGeneralize::createPointCollection()
{
  SpatialReference sr(32126);
  PointCollection* pointCollection = new PointCollection(sr, this);
  pointCollection->addPoint(2330611.130549, 202360.002957, 0.000000);
  pointCollection->addPoint(2330583.834672, 202525.984012, 0.000000);
  pointCollection->addPoint(2330574.164902, 202691.488009, 0.000000);
  pointCollection->addPoint(2330689.292623, 203170.045888, 0.000000);
  pointCollection->addPoint(2330696.773344, 203317.495798, 0.000000);
  pointCollection->addPoint(2330691.419723, 203380.917080, 0.000000);
  pointCollection->addPoint(2330435.065296, 203816.662457, 0.000000);
  pointCollection->addPoint(2330369.500800, 204329.861789, 0.000000);
  pointCollection->addPoint(2330400.929891, 204712.129673, 0.000000);
  pointCollection->addPoint(2330484.300447, 204927.797132, 0.000000);
  pointCollection->addPoint(2330514.469919, 205000.792463, 0.000000);
  pointCollection->addPoint(2330638.099138, 205271.601116, 0.000000);
  pointCollection->addPoint(2330725.315888, 205631.231308, 0.000000);
  pointCollection->addPoint(2330755.640702, 206433.354860, 0.000000);
  pointCollection->addPoint(2330680.644719, 206660.240923, 0.000000);
  pointCollection->addPoint(2330386.957926, 207340.947204, 0.000000);
  pointCollection->addPoint(2330485.861737, 207742.298501, 0.000000);
  return pointCollection;
}

void DensifyAndGeneralize::showResults(bool show)
{
  m_resultMultipointGraphic->setVisible(show);
  m_resultLineGraphic->setVisible(show);
}

// [WriteFile Name=DensifyAndGeneralize, Category=Geometry]
// [Legal]
// Copyright 2018 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]

#ifndef DENSIFYANDGENERALIZE_H
#define DENSIFYANDGENERALIZE_H

// Qt headers
#include <QQuickItem>

// STL headers
#include <PointCollection.h>

namespace Esri::ArcGISRuntime
{
class Map;
class MapQuickView;
class GraphicsOverlay;
class Graphic;
class PointCollection;
}

class DensifyAndGeneralize : public QQuickItem
{
  Q_OBJECT

public:
  explicit DensifyAndGeneralize(QQuickItem* parent = nullptr);
  ~DensifyAndGeneralize() override = default;

  void componentComplete() override;
  static void init();
  Q_INVOKABLE void updateGeometry(bool densify, double maxSegmentLength, bool generalize, double maxDeviation);
  Q_INVOKABLE void showResults(bool show);

private:
  Esri::ArcGISRuntime::Map* m_map = nullptr;
  Esri::ArcGISRuntime::MapQuickView* m_mapView = nullptr;
  Esri::ArcGISRuntime::GraphicsOverlay* m_graphicsOverlay = nullptr;
  Esri::ArcGISRuntime::Graphic* m_originalMultipointGraphic = nullptr;
  Esri::ArcGISRuntime::Graphic* m_originalLineGraphic = nullptr;
  Esri::ArcGISRuntime::Graphic* m_resultMultipointGraphic = nullptr;
  Esri::ArcGISRuntime::Graphic* m_resultLineGraphic = nullptr;

  Esri::ArcGISRuntime::PointCollection* createPointCollection();
};

#endif // DENSIFYANDGENERALIZE_H

// [WriteFile Name=DensifyAndGeneralize, Category=Geometry]
// [Legal]
// Copyright 2018 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]

import QtQuick
import QtQuick.Window
import QtQuick.Controls
import Esri.Samples

DensifyAndGeneralizeSample {
    id: rootRectangle
    clip: true
    width: 800
    height: 600



    // add a mapView component
    MapView {
        anchors.fill: parent
        objectName: "mapView"

        Component.onCompleted: {
            // Set the focus on MapView to initially enable keyboard navigation
            forceActiveFocus();
        }
    }

    Rectangle {
        anchors {
            fill: controlColumn
            margins: -5
        }
        color: "#f9f9f9"
        radius: 5
    }

    Column {
        id: controlColumn
        anchors {
            left: parent.left
            top: parent.top
            margins: 10
        }
        spacing: 5


        CheckBox {
            id: densifyCheckbox
            text: "Densify"
            checked: true
        }

        Text {
            text: "Max segment length"
            enabled: densifyCheckbox.checked
        }

        Slider {
            id: maxSegmentLengthSlider
            from: 100
            to: 500
            width: 175
            value: 100
            onValueChanged: updateGeometry(densifyCheckbox.checked, maxSegmentLengthSlider.value, generalizeCheckbox.checked, maxDeviationSlider.value);
        }

        CheckBox {
            id: generalizeCheckbox
            text: "Generalize"
            checked: true
        }

        Text {
            text: "Max deviation"
            enabled: generalizeCheckbox.checked
        }

        Slider {
            id: maxDeviationSlider
            from: 1
            to: 250
            width: 175
            onValueChanged: updateGeometry(densifyCheckbox.checked, maxSegmentLengthSlider.value, generalizeCheckbox.checked, maxDeviationSlider.value);
        }

        CheckBox {
            id: showResultCheckbox
            text: "Show Result"
            checked: true
            onCheckedChanged: showResults(checked);
        }
    }
}

// [Legal]
// Copyright 2018 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]

// sample headers
#include "DensifyAndGeneralize.h"

// ArcGIS Maps SDK headers
#include "ArcGISRuntimeEnvironment.h"

// Qt headers
#include <QCommandLineParser>
#include <QDir>
#include <QGuiApplication>
#include <QQmlEngine>
#include <QQuickView>

// Platform specific headers
#ifdef Q_OS_WIN
#include <Windows.h>
#endif

#define STRINGIZE(x) #x
#define QUOTE(x) STRINGIZE(x)

int main(int argc, char *argv[])
{
  Esri::ArcGISRuntime::ArcGISRuntimeEnvironment::setUseLegacyAuthentication(false);
  QGuiApplication app(argc, argv);

  // Use of ArcGIS location services, such as basemap styles, geocoding, and routing services,
  // requires an access token. For more information see
  // https://links.esri.com/arcgis-runtime-security-auth.

  // The following methods grant an access token:

  // 1. User authentication: Grants a temporary access token associated with a user's ArcGIS account.
  // To generate a token, a user logs in to the app with an ArcGIS account that is part of an
  // organization in ArcGIS Online or ArcGIS Enterprise.

  // 2. API key authentication: Get a long-lived access token that gives your application access to
  // ArcGIS location services. Go to the tutorial at https://links.esri.com/create-an-api-key.
  // Copy the API Key access token.

  const QString accessToken = QString("");

  if (accessToken.isEmpty())
  {
      qWarning() << "Use of ArcGIS location services, such as the basemap styles service, requires" <<
                    "you to authenticate with an ArcGIS account or set the API Key property.";
  }
  else
  {
      Esri::ArcGISRuntime::ArcGISRuntimeEnvironment::setApiKey(accessToken);
  }

  // Initialize the sample
  DensifyAndGeneralize::init();

  // Initialize application view
  QQuickView view;
  view.setResizeMode(QQuickView::SizeRootObjectToView);

  QString arcGISRuntimeImportPath = QUOTE(ARCGIS_RUNTIME_IMPORT_PATH);

#if defined(LINUX_PLATFORM_REPLACEMENT)
  // on some linux platforms the string 'linux' is replaced with 1
  // fix the replacement paths which were created
  QString replaceString = QUOTE(LINUX_PLATFORM_REPLACEMENT);
  arcGISRuntimeImportPath = arcGISRuntimeImportPath.replace(replaceString, "linux", Qt::CaseSensitive);
#endif

  // Add the import Path
  view.engine()->addImportPath(QDir(QCoreApplication::applicationDirPath()).filePath("qml"));
  // Add the Runtime and Extras path
  view.engine()->addImportPath(arcGISRuntimeImportPath);

  // Set the source
  view.setSource(QUrl("qrc:/Samples/Geometry/DensifyAndGeneralize/DensifyAndGeneralize.qml"));

  view.show();

  return app.exec();
}

Use case

How to use the sample

How it works

Relevant API

Tags

Sample Code