qgsalgorithmextractvertices.cpp

Go to the documentation of this file.

/***************************************************************************
                         qgsalgorithmextractvertices.cpp
                         --------------------------
    begin                : November 2017
    copyright            : (C) 2017 by Mathieu Pellerin
    email                : nirvn dot asia 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 "qgsalgorithmextractvertices.h"

#include "qgsabstractgeometry.h"
#include "qgsgeometryutils.h"


QString QgsExtractVerticesAlgorithm::name() const
{
  return QStringLiteral( "extractvertices" );
}

QString QgsExtractVerticesAlgorithm::displayName() const
{
  return QObject::tr( "Extract vertices" );
}

QStringList QgsExtractVerticesAlgorithm::tags() const
{
  return QObject::tr( "points,vertex,nodes" ).split( ',' );
}

QString QgsExtractVerticesAlgorithm::group() const
{
  return QObject::tr( "Vector geometry" );
}

QString QgsExtractVerticesAlgorithm::groupId() const
{
  return QStringLiteral( "vectorgeometry" );
}

QString QgsExtractVerticesAlgorithm::shortHelpString() const
{
  return QObject::tr( "This algorithm takes a line or polygon layer and generates a point layer with points representing the vertices in the input lines or polygons. The attributes associated to each point are the same ones associated to the line or polygon that the point belongs to." ) +
         QStringLiteral( "\n\n" )  +
         QObject::tr( "Additional fields are added to the point indicating the vertex index (beginning at 0), the vertex’s part and its index within the part (as well as its ring for polygons), distance along original geometry and bisector angle of vertex for original geometry." );
}

QgsExtractVerticesAlgorithm *QgsExtractVerticesAlgorithm::createInstance() const
{
  return new QgsExtractVerticesAlgorithm();
}

void QgsExtractVerticesAlgorithm::initAlgorithm( const QVariantMap & )
{
  addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ) ) );

  addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Vertices" ) ) );
}

QVariantMap QgsExtractVerticesAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  std::unique_ptr< QgsProcessingFeatureSource > featureSource( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
  if ( !featureSource )
    throw QgsProcessingException( QObject::tr( "Could not load source layer for INPUT" ) );

  QgsWkbTypes::Type outputWkbType = QgsWkbTypes::Point;
  if ( QgsWkbTypes::hasM( featureSource->wkbType() ) )
  {
    outputWkbType = QgsWkbTypes::addM( outputWkbType );
  }
  if ( QgsWkbTypes::hasZ( featureSource->wkbType() ) )
  {
    outputWkbType = QgsWkbTypes::addZ( outputWkbType );
  }

  QgsFields outputFields = featureSource->fields();
  outputFields.append( QgsField( QStringLiteral( "vertex_index" ), QVariant::Int, QString(), 10, 0 ) );
  outputFields.append( QgsField( QStringLiteral( "vertex_part" ), QVariant::Int, QString(), 10, 0 ) );
  if ( QgsWkbTypes::geometryType( featureSource->wkbType() ) == QgsWkbTypes::PolygonGeometry )
  {
    outputFields.append( QgsField( QStringLiteral( "vertex_part_ring" ), QVariant::Int, QString(), 10, 0 ) );
  }
  outputFields.append( QgsField( QStringLiteral( "vertex_part_index" ), QVariant::Int, QString(), 10, 0 ) );
  outputFields.append( QgsField( QStringLiteral( "distance" ), QVariant::Double, QString(), 20, 14 ) );
  outputFields.append( QgsField( QStringLiteral( "angle" ), QVariant::Double, QString(), 20, 14 ) );

  QString dest;
  std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, outputFields, outputWkbType, featureSource->sourceCrs() ) );
  if ( !sink )
    throw QgsProcessingException( QObject::tr( "Could not create destination layer for OUTPUT" ) );;

  double step = featureSource->featureCount() > 0 ? 100.0 / featureSource->featureCount() : 1;
  QgsFeatureIterator fi = featureSource->getFeatures( QgsFeatureRequest(), QgsProcessingFeatureSource::FlagSkipGeometryValidityChecks );
  QgsFeature f;
  int i = -1;
  while ( fi.nextFeature( f ) )
  {
    i++;
    if ( feedback->isCanceled() )
    {
      break;
    }

    QgsGeometry inputGeom = f.geometry();
    if ( inputGeom.isNull() )
    {
      sink->addFeature( f, QgsFeatureSink::FastInsert );
    }
    else
    {
      QgsAbstractGeometry::vertex_iterator vi = inputGeom.constGet()->vertices_begin();
      double cumulativeDistance = 0.0;
      int vertexPos = 0;
      while ( vi != inputGeom.constGet()->vertices_end() )
      {
        QgsVertexId vertexId = vi.vertexId();
        double angle = inputGeom.constGet()->vertexAngle( vertexId ) * 180 / M_PI;
        QgsAttributes attrs = f.attributes();
        attrs << vertexPos
              << vertexId.part;
        if ( QgsWkbTypes::geometryType( featureSource->wkbType() ) == QgsWkbTypes::PolygonGeometry )
        {
          attrs << vertexId.ring;
        }
        attrs << vertexId.vertex
              << cumulativeDistance
              << angle;
        QgsFeature outputFeature = QgsFeature();
        outputFeature.setAttributes( attrs );
        outputFeature.setGeometry( QgsGeometry( ( *vi ).clone() ) );
        sink->addFeature( outputFeature, QgsFeatureSink::FastInsert );
        vi++;
        vertexPos++;

        // calculate distance to next vertex
        double distanceToNext = inputGeom.constGet()->segmentLength( vertexId );
        cumulativeDistance += distanceToNext;
      }
    }
    feedback->setProgress( i * step );
  }

  QVariantMap outputs;
  outputs.insert( QStringLiteral( "OUTPUT" ), dest );
  return outputs;
}