qgsalgorithmdelaunaytriangulation.cpp

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/***************************************************************************
                         qgsalgorithmdelaunaytriangulation.cpp
                         ---------------------
    begin                : July 2023
    copyright            : (C) 2023 by Alexander Bruy
    email                : alexander dot bruy at gmail dot com
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgsalgorithmdelaunaytriangulation.h"
#include "qgsspatialindex.h"
#include "qgsmultipoint.h"
#include "qgsattributes.h"
 
 
QString QgsDelaunayTriangulationAlgorithm::name() const
{
  return QStringLiteral( "delaunaytriangulation" );
}
 
QString QgsDelaunayTriangulationAlgorithm::displayName() const
{
  return QObject::tr( "Delaunay triangulation" );
}
 
QStringList QgsDelaunayTriangulationAlgorithm::tags() const
{
  return QObject::tr( "delaunay,triangulation,polygons,voronoi" ).split( ',' );
}
 
QString QgsDelaunayTriangulationAlgorithm::group() const
{
  return QObject::tr( "Vector geometry" );
}
 
QString QgsDelaunayTriangulationAlgorithm::groupId() const
{
  return QStringLiteral( "vectorgeometry" );
}
 
QString QgsDelaunayTriangulationAlgorithm::shortHelpString() const
{
  return QObject::tr( "Creates a polygon layer with the Delaunay triangulation corresponding to a points layer." );
}
 
QgsDelaunayTriangulationAlgorithm *QgsDelaunayTriangulationAlgorithm::createInstance() const
{
  return new QgsDelaunayTriangulationAlgorithm();
}
 
void QgsDelaunayTriangulationAlgorithm::initAlgorithm( const QVariantMap & )
{
  addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ), QList< int >() << QgsProcessing::TypeVectorPoint ) );
  std::unique_ptr<QgsProcessingParameterNumber> toleranceParam = std::make_unique<QgsProcessingParameterNumber>( QStringLiteral( "TOLERANCE" ), QObject::tr( "Tolerance" ), QgsProcessingParameterNumber::Double, 0, true, 0 );
  toleranceParam->setHelp( QObject::tr( "Specifies an optional snapping tolerance which can be used to improve the robustness of the triangulation" ) );
  addParameter( toleranceParam.release() );
  addParameter( new QgsProcessingParameterBoolean( QStringLiteral( "ADD_ATTRIBUTES" ), QObject::tr( "Add point IDs to output" ), true ) );
  addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Delaunay triangulation" ), QgsProcessing::TypeVectorPolygon ) );
}
 
QVariantMap QgsDelaunayTriangulationAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
  if ( !source )
    throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
 
  if ( source->featureCount() < 3 )
    throw QgsProcessingException( QObject::tr( "Input layer should contain at least 3 points." ) );
 
  const double tolerance = parameterAsDouble( parameters, QStringLiteral( "TOLERANCE" ), context );
  const bool addAttributes = parameterAsBool( parameters, QStringLiteral( "ADD_ATTRIBUTES" ), context );
 
  QgsFields fields;
  if ( addAttributes )
  {
    fields.append( QgsField( QStringLiteral( "POINTA" ), QVariant::LongLong ) );
    fields.append( QgsField( QStringLiteral( "POINTB" ), QVariant::LongLong ) );
    fields.append( QgsField( QStringLiteral( "POINTC" ), QVariant::LongLong ) );
  }
  else
  {
    fields.append( QgsField( QStringLiteral( "id" ), QVariant::LongLong ) );
  }
 
  QString dest;
  std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, fields, Qgis::WkbType::Polygon, source->sourceCrs() ) );
  if ( !sink )
    throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
 
  QgsFeatureIterator it = source->getFeatures( QgsFeatureRequest().setNoAttributes(), QgsProcessingFeatureSource::FlagSkipGeometryValidityChecks );
 
  QgsGeometry allPoints;
 
  long long i = 0;
  const double step = source->featureCount() > 0 ? 50.0 / source->featureCount() : 1;
 
  const QgsSpatialIndex index( it, [&]( const QgsFeature & f )->bool
  {
    i++;
    if ( feedback->isCanceled() )
      return false;
 
    feedback->setProgress( i * step );
 
    if ( !f.hasGeometry() )
      return true;
 
    const QgsAbstractGeometry *geom = f.geometry().constGet();
    if ( QgsWkbTypes::isMultiType( geom->wkbType() ) )
    {
      const QgsMultiPoint mp( *qgsgeometry_cast< const QgsMultiPoint * >( geom ) );
      for ( auto pit = mp.const_parts_begin(); pit != mp.const_parts_end(); ++pit )
      {
        allPoints.addPart( qgsgeometry_cast< QgsPoint * >( *pit )->clone(), Qgis::GeometryType::Point );
      }
    }
    else
    {
      allPoints.addPart( qgsgeometry_cast< QgsPoint * >( geom )->clone(), Qgis::GeometryType::Point );
    }
 
    return true;
  }, QgsSpatialIndex::FlagStoreFeatureGeometries );
 
  const QgsGeometry triangulation = allPoints.delaunayTriangulation( tolerance );
 
  if ( !triangulation.isEmpty() )
  {
    const QVector< QgsGeometry > collection = triangulation.asGeometryCollection();
    for ( int i = 0; i < collection.length(); i++ )
    {
      if ( feedback->isCanceled() )
      {
        break;
      }
      QgsFeature f;
      f.setFields( fields );
      f.setGeometry( collection[ i ] );
      if ( addAttributes )
      {
        const QList< QgsFeatureId > nearest = index.nearestNeighbor( collection[i], 3 );
        QgsAttributes attrs;
        for ( int j = 0; j < 3; j++ )
        {
          attrs << nearest.at( j );
        }
        f.setAttributes( attrs );
      }
      else
      {
        f.setAttributes( QgsAttributes() << i );
      }
 
      if ( !sink->addFeature( f, QgsFeatureSink::FastInsert ) )
        throw QgsProcessingException( writeFeatureError( sink.get(), parameters, QStringLiteral( "OUTPUT" ) ) );
      feedback->setProgress( 50 + i * step );
    }
  }
 
  QVariantMap outputs;
  outputs.insert( QStringLiteral( "OUTPUT" ), dest );
  return outputs;
}