qgsalgorithmtininterpolation.cpp

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/***************************************************************************
                         qgsalgorithmtininterpolation.cpp
                         -----------------------------------
    begin                : August 2026
    copyright            : (C) 2026 by Nyall Dawson
    email                : nyall dot dawson 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 "qgsalgorithmtininterpolation.h"
 
#include "qgsgridfilewriter.h"
#include "qgsprocessingparameterinterpolationpixelsize.h"
#include "qgsprocessingparameterinterpolationsource.h"
#include "qgsprocessingutils.h"
#include "qgstininterpolator.h"
 
#include <QString>
 
using namespace Qt::StringLiterals;

QgsTinInterpolationAlgorithm::QgsTinInterpolationAlgorithm() = default;
 
QString QgsTinInterpolationAlgorithm::name() const
{
  return u"tininterpolation"_s;
}
 
QString QgsTinInterpolationAlgorithm::displayName() const
{
  return QObject::tr( "TIN interpolation" );
}
 
QStringList QgsTinInterpolationAlgorithm::tags() const
{
  return QObject::tr( "tin,triangulated,irregular,network,delaunay,interpolation,surface,breaklines,breaks,structures" ).split( ',' );
}
 
QString QgsTinInterpolationAlgorithm::group() const
{
  return QObject::tr( "Interpolation" );
}
 
QString QgsTinInterpolationAlgorithm::groupId() const
{
  return u"interpolation"_s;
}
 
QString QgsTinInterpolationAlgorithm::shortDescription() const
{
  return QObject::tr( "Generates a Triangulated Irregular Network (TIN) interpolation from vector layers." );
}
 
QString QgsTinInterpolationAlgorithm::shortHelpString() const
{
  return QObject::tr(
    "This algorithm generates a Triangulated Irregular Network (TIN) interpolation surface raster from one or more vector layers.\n\n"
    "The TIN method constructs a Delaunay triangulation network from sample features. Surfaces within the constructed triangles "
    "are interpolated using either Linear or Clough-Tocher (cubic) methods. To do this, circumcircles around selected "
    "sample points are created and their intersections are connected to a network of non overlapping and as compact "
    "as possible triangles.\n\n"
    "Input layers can supply sample values from feature attributes or feature Z coordinates. Features can be specified as discrete "
    "points, structure lines, or breaklines.\n\n"
    "Optionally, the algorithm can also output a vector line layer representing the triangulation network boundaries."
  );
}
 
QgsTinInterpolationAlgorithm *QgsTinInterpolationAlgorithm::createInstance() const
{
  return new QgsTinInterpolationAlgorithm();
}
 
void QgsTinInterpolationAlgorithm::initAlgorithm( const QVariantMap & )
{
  auto dataParam = std::make_unique<QgsProcessingParameterInterpolationSource>( u"INTERPOLATION_DATA"_s, QObject::tr( "Input layer(s)" ) );
  dataParam->setHelp( QObject::tr( "Vector layers to use for triangulation along with their attributes and source types." ) );
  addParameter( dataParam.release() );
 
  const QStringList methods = { QObject::tr( "Linear" ), QObject::tr( "Clough-Toucher (cubic)" ) };
  auto methodParam = std::make_unique<QgsProcessingParameterEnum>( u"METHOD"_s, QObject::tr( "Interpolation method" ), methods, false, 0 );
  methodParam->setHelp( QObject::tr( "Method used to interpolate values within constructed triangles." ) );
  addParameter( methodParam.release() );
 
  auto extentParam = std::make_unique<QgsProcessingParameterExtent>( u"EXTENT"_s, QObject::tr( "Extent" ), QVariant(), false );
  extentParam->setHelp( QObject::tr( "Bounding box defining output raster extent." ) );
  addParameter( extentParam.release() );
 
  auto pixelSizeParam = std::make_unique<QgsProcessingParameterInterpolationPixelSize>( u"PIXEL_SIZE"_s, QObject::tr( "Output raster size" ), u"INTERPOLATION_DATA"_s, u"EXTENT"_s, 0.1 );
  pixelSizeParam->setHelp( QObject::tr( "Pixel size in layer units used to calculate output grid dimensions." ) );
  addParameter( pixelSizeParam.release() );
 
  auto colsParam = std::make_unique<QgsProcessingParameterNumber>( u"COLUMNS"_s, QObject::tr( "Number of columns" ), Qgis::ProcessingNumberParameterType::Integer, QVariant(), true, 0, 10000000 );
  colsParam->setFlags( colsParam->flags() | Qgis::ProcessingParameterFlag::Hidden );
  addParameter( colsParam.release() );
 
  auto rowsParam = std::make_unique<QgsProcessingParameterNumber>( u"ROWS"_s, QObject::tr( "Number of rows" ), Qgis::ProcessingNumberParameterType::Integer, QVariant(), true, 0, 10000000 );
  rowsParam->setFlags( rowsParam->flags() | Qgis::ProcessingParameterFlag::Hidden );
  addParameter( rowsParam.release() );
 
  auto outputNodataParam = std::make_unique<QgsProcessingParameterNumber>( u"NODATA"_s, QObject::tr( "Output NoData value" ), Qgis::ProcessingNumberParameterType::Double, -9999.0 );
  outputNodataParam->setHelp( QObject::tr( "The NODATA value to use in the output raster." ) );
  outputNodataParam->setFlags( outputNodataParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( outputNodataParam.release() );
 
  auto creationOptsParam = std::make_unique<QgsProcessingParameterString>( u"CREATION_OPTIONS"_s, QObject::tr( "Creation options" ), QVariant(), false, true );
  creationOptsParam->setHelp( QObject::tr( "The raster creation options for the output raster. These options control things like colorimetry, compression, etc." ) );
  creationOptsParam->setMetadata( QVariantMap( { { u"widget_wrapper"_s, QVariantMap( { { u"widget_type"_s, u"rasteroptions"_s } } ) } } ) );
  creationOptsParam->setFlags( creationOptsParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( creationOptsParam.release() );
 
  auto outputParam = std::make_unique<QgsProcessingParameterRasterDestination>( u"OUTPUT"_s, QObject::tr( "Interpolated" ) );
  addParameter( outputParam.release() );
 
  auto triangulationParam = std::make_unique<QgsProcessingParameterFeatureSink>( u"TRIANGULATION"_s, QObject::tr( "Triangulation" ), Qgis::ProcessingSourceType::VectorLine, QVariant(), true );
  triangulationParam->setCreateByDefault( false );
  triangulationParam->setHelp( QObject::tr( "Optional output vector layer to save triangulation network lines." ) );
  addParameter( triangulationParam.release() );
}
 
QVariantMap QgsTinInterpolationAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  QGS_MARK_ALGORITHM_SOURCE
 
  const QString interpolationData = parameterAsString( parameters, u"INTERPOLATION_DATA"_s, context );
  const int method = parameterAsEnum( parameters, u"METHOD"_s, context );
  const QgsRectangle boundingBox = parameterAsExtent( parameters, u"EXTENT"_s, context );
  const double pixelSize = parameterAsDouble( parameters, u"PIXEL_SIZE"_s, context );
  const QString creationOptions = parameterAsString( parameters, u"CREATION_OPTIONS"_s, context ).trimmed();
  const double outputNodata = parameterAsDouble( parameters, u"NODATA"_s, context );
  const QString output = parameterAsOutputLayer( parameters, u"OUTPUT"_s, context );
 
  int columns = parameterAsInt( parameters, u"COLUMNS"_s, context );
  int rows = parameterAsInt( parameters, u"ROWS"_s, context );
  if ( columns == 0 )
  {
    columns = std::max( static_cast<int>( std::ceil( boundingBox.width() / pixelSize ) ), 1 );
  }
  if ( rows == 0 )
  {
    rows = std::max( static_cast<int>( std::ceil( boundingBox.height() / pixelSize ) ), 1 );
  }
 
  if ( interpolationData.isEmpty() )
  {
    throw QgsProcessingException( QObject::tr( "At least one input layer must be specified." ) );
  }
 
  QList<QgsInterpolator::LayerData> layerDataList;
  std::vector<std::unique_ptr<QgsFeatureSource>> sourceHolders;
  QgsCoordinateReferenceSystem layerCrs;
 
  const QStringList layerRows = interpolationData.split( "::|::"_L1, Qt::SkipEmptyParts );
  for ( const QString &row : std::as_const( layerRows ) )
  {
    const QStringList tokens = row.split( "::~::"_L1 );
    if ( tokens.size() < 4 )
    {
      continue;
    }
 
    QgsInterpolator::LayerData data;
    std::unique_ptr<QgsProcessingFeatureSource> source( QgsProcessingUtils::variantToSource( tokens.at( 0 ), context ) );
 
    if ( !source )
    {
      throw QgsProcessingException( QObject::tr( "Could not load source layer for input %1." ).arg( tokens.at( 0 ) ) );
    }
 
    data.source = source.get();
    data.transformContext = context.transformContext();
 
    if ( !layerCrs.isValid() )
    {
      layerCrs = source->sourceCrs();
    }
 
    data.valueSource = static_cast<Qgis::InterpolationValueSource>( tokens.at( 1 ).toInt() );
 
    bool intOk = false;
    data.interpolationAttribute = tokens.at( 2 ).toInt( &intOk );
 
    if ( data.valueSource == Qgis::InterpolationValueSource::Attribute )
    {
      if ( !intOk )
      {
        data.interpolationAttribute = source->fields().lookupField( tokens.at( 2 ) );
        if ( data.interpolationAttribute < 0 )
        {
          throw QgsProcessingException( QObject::tr( "Field %1 does not exist in layer %2." ).arg( tokens.at( 2 ), source->sourceName() ) );
        }
      }
      else if ( data.interpolationAttribute < 0 )
      {
        throw QgsProcessingException( QObject::tr( "Layer %1 is set to use a value attribute, but no attribute was set." ).arg( source->sourceName() ) );
      }
      else if ( data.interpolationAttribute >= source->fields().size() )
      {
        throw QgsProcessingException( QObject::tr( "Layer %1 is set to use an invalid attribute." ).arg( source->sourceName() ) );
      }
    }
 
    data.sourceType = static_cast<Qgis::InterpolationSourceType>( tokens.at( 3 ).toInt() );
 
    layerDataList.append( data );
    sourceHolders.push_back( std::move( source ) );
  }
 
  const QgsTinInterpolator::TinInterpolation tinMethod = ( method == 0 ) ? QgsTinInterpolator::TinInterpolation::Linear : QgsTinInterpolator::TinInterpolation::CloughTocher;
 
  QString triangulationDestinationId;
  std::unique_ptr<QgsFeatureSink> triangulationSink(
    parameterAsSink( parameters, u"TRIANGULATION"_s, context, triangulationDestinationId, QgsTinInterpolator::triangulationFields(), Qgis::WkbType::LineString, layerCrs )
  );
 
  QgsTinInterpolator interpolator( layerDataList, tinMethod, feedback );
  if ( triangulationSink )
  {
    interpolator.setTriangulationSink( triangulationSink.get() );
  }
 
  QgsGridFileWriter writer( &interpolator, output, boundingBox, columns, rows );
  if ( !creationOptions.isEmpty() )
  {
    writer.setCreationOptions( creationOptions.split( '|' ) );
  }
  writer.setNoDataValue( outputNodata );
  writer.writeFile( feedback );
 
  if ( triangulationSink )
  {
    triangulationSink->finalize();
    if ( feedback )
    {
      feedback->featureSinkFinalized( u"TRIANGULATION"_s );
    }
  }
 
  QVariantMap outputs;
  outputs.insert( u"OUTPUT"_s, output );
  if ( triangulationSink )
  {
    outputs.insert( u"TRIANGULATION"_s, triangulationDestinationId );
  }
  return outputs;
}