qgsalgorithmdownloadvectortiles.cpp

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/***************************************************************************
                         qgsalgorithmdownloadvectortiles.cpp
                         ---------------------
    begin                : May 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 "qgsalgorithmdownloadvectortiles.h"
 
#include "qgsmbtiles.h"
#include "qgsvectortilelayer.h"
#include "qgsvectortileloader.h"
#include "qgsziputils.h"
 
#include <QString>
 
using namespace Qt::StringLiterals;

 
class SetStylePostProcessor : public QgsProcessingLayerPostProcessorInterface
{
  public:
    SetStylePostProcessor( QDomDocument &doc )
      : mDocument( doc )
    {}
 
    void postProcessLayer( QgsMapLayer *layer, QgsProcessingContext &, QgsProcessingFeedback * ) override
    {
      if ( QgsVectorTileLayer *tileLayer = qobject_cast<QgsVectorTileLayer *>( layer ) )
      {
        QString errorMsg;
        tileLayer->importNamedStyle( mDocument, errorMsg );
        tileLayer->triggerRepaint();
      }
    }
 
  private:
    QDomDocument mDocument;
};
 
QString QgsDownloadVectorTilesAlgorithm::name() const
{
  return u"downloadvectortiles"_s;
}
 
QString QgsDownloadVectorTilesAlgorithm::displayName() const
{
  return QObject::tr( "Download vector tiles" );
}
 
QStringList QgsDownloadVectorTilesAlgorithm::tags() const
{
  return QObject::tr( "vector,split,field,unique" ).split( ',' );
}
 
QString QgsDownloadVectorTilesAlgorithm::group() const
{
  return QObject::tr( "Vector tiles" );
}
 
QString QgsDownloadVectorTilesAlgorithm::groupId() const
{
  return u"vectortiles"_s;
}
 
QString QgsDownloadVectorTilesAlgorithm::shortHelpString() const
{
  return QObject::tr( "This algorithm downloads vector tiles of the input vector tile layer and saves them in the local vector tile file." );
}
 
QString QgsDownloadVectorTilesAlgorithm::shortDescription() const
{
  return QObject::tr( "Downloads vector tiles of the input vector tile layer and saves them in the local vector tile file." );
}
 
QgsDownloadVectorTilesAlgorithm *QgsDownloadVectorTilesAlgorithm::createInstance() const
{
  return new QgsDownloadVectorTilesAlgorithm();
}
 
void QgsDownloadVectorTilesAlgorithm::initAlgorithm( const QVariantMap & )
{
  addParameter( new QgsProcessingParameterMapLayer( u"INPUT"_s, QObject::tr( "Input layer" ), QVariant(), false, QList<int>() << static_cast<int>( Qgis::ProcessingSourceType::VectorTile ) ) );
  addParameter( new QgsProcessingParameterExtent( u"EXTENT"_s, QObject::tr( "Extent" ) ) );
  addParameter( new QgsProcessingParameterNumber( u"MAX_ZOOM"_s, QObject::tr( "Maximum zoom level to download" ), Qgis::ProcessingNumberParameterType::Integer, 10, false, 0 ) );
  addParameter( new QgsProcessingParameterNumber( u"TILE_LIMIT"_s, QObject::tr( "Tile limit" ), Qgis::ProcessingNumberParameterType::Integer, 100, false, 0 ) );
  addParameter( new QgsProcessingParameterVectorTileDestination( u"OUTPUT"_s, QObject::tr( "Output" ) ) );
}
 
bool QgsDownloadVectorTilesAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  QgsMapLayer *layer = parameterAsLayer( parameters, u"INPUT"_s, context );
  if ( !layer )
    throw QgsProcessingException( QObject::tr( "Invalid input layer" ) );
 
  QgsVectorTileLayer *vtLayer = qobject_cast<QgsVectorTileLayer *>( layer );
  mProvider.reset( qgis::down_cast<const QgsVectorTileDataProvider *>( vtLayer->dataProvider() )->clone() );
  mTileMatrixSet = vtLayer->tileMatrixSet();
  mSourceMinZoom = vtLayer->sourceMinZoom();
  mLayerName = vtLayer->name();
 
  mExtent = parameterAsExtent( parameters, u"EXTENT"_s, context, layer->crs() );
 
  mMaxZoom = parameterAsInt( parameters, u"MAX_ZOOM"_s, context );
  if ( mMaxZoom > vtLayer->sourceMaxZoom() )
  {
    throw QgsProcessingException( QObject::tr( "Requested maximum zoom level is bigger than available zoom level in the source layer. Please, select zoom level lower or equal to %1." ).arg( vtLayer->sourceMaxZoom() ) );
  }
 
  mTileLimit = static_cast<long long>( parameterAsInt( parameters, u"TILE_LIMIT"_s, context ) );
 
  mStyleDocument = QDomDocument( u"qgis"_s );
  QString errorMsg;
  vtLayer->exportNamedStyle( mStyleDocument, errorMsg );
  if ( !errorMsg.isEmpty() )
  {
    feedback->pushWarning( QObject::tr( "Failed to get layer style: %1" ).arg( errorMsg ) );
  }
 
  return true;
}
 
QVariantMap QgsDownloadVectorTilesAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  const QString outputFile = parameterAsOutputLayer( parameters, u"OUTPUT"_s, context );
 
  // count total number of tiles in the requested extent and zoom levels to see if it exceeds the tile limit
  long long tileCount = 0;
  QMap<int, QgsTileRange> tileRanges;
  for ( int i = 0; i <= mMaxZoom; i++ )
  {
    QgsTileMatrix tileMatrix = mTileMatrixSet.tileMatrix( i );
    QgsTileRange tileRange = tileMatrix.tileRangeFromExtent( mExtent );
    tileRanges.insert( i, tileRange );
    tileCount += static_cast<long long>( tileRange.endColumn() - tileRange.startColumn() + 1 ) * ( tileRange.endRow() - tileRange.startRow() + 1 );
  }
  if ( tileCount > mTileLimit )
  {
    throw QgsProcessingException( QObject::tr( "Requested number of tiles %1 exceeds limit of %2 tiles. Please, select a smaller extent, reduce maximum zoom level or increase tile limit." ).arg( tileCount ).arg( mTileLimit ) );
  }
 
  auto writer = std::make_unique<QgsMbTiles>( outputFile );
  if ( !writer->create() )
  {
    throw QgsProcessingException( QObject::tr( "Failed to create MBTiles file %1" ).arg( outputFile ) );
  }
  writer->setMetadataValue( "format", "pbf" );
  writer->setMetadataValue( "name", mLayerName );
  writer->setMetadataValue( "minzoom", QString::number( mSourceMinZoom ) );
  writer->setMetadataValue( "maxzoom", QString::number( mMaxZoom ) );
  writer->setMetadataValue( "crs", mTileMatrixSet.rootMatrix().crs().authid() );
  try
  {
    QgsCoordinateTransform ct( mTileMatrixSet.rootMatrix().crs(), QgsCoordinateReferenceSystem( "EPSG:4326" ), context.transformContext() );
    ct.setBallparkTransformsAreAppropriate( true );
    QgsRectangle wgsExtent = ct.transformBoundingBox( mExtent );
    QString boundsStr = QString( "%1,%2,%3,%4" )
                          .arg( wgsExtent.xMinimum() )
                          .arg( wgsExtent.yMinimum() )
                          .arg( wgsExtent.xMaximum() )
                          .arg( wgsExtent.yMaximum() );
    writer->setMetadataValue( "bounds", boundsStr );
  }
  catch ( const QgsCsException & )
  {
    // bounds won't be written (not a problem - it is an optional value)
  }
 
  QgsProcessingMultiStepFeedback multiStepFeedback( mMaxZoom + 1, feedback );
 
  std::unique_ptr<QgsVectorTileLoader> loader;
  QList<QgsVectorTileRawData> rawTiles;
 
  QMap<int, QgsTileRange>::const_iterator it = tileRanges.constBegin();
  while ( it != tileRanges.constEnd() )
  {
    if ( feedback->isCanceled() )
      break;
 
    multiStepFeedback.setCurrentStep( it.key() );
 
    QgsTileMatrix tileMatrix = mTileMatrixSet.tileMatrix( it.key() );
    tileCount = static_cast<long long>( it.value().endColumn() - it.value().startColumn() + 1 ) * ( it.value().endRow() - it.value().startRow() + 1 );
 
    const QPointF viewCenter = tileMatrix.mapToTileCoordinates( mExtent.center() );
 
    long long tileNumber = 0;
    rawTiles = QgsVectorTileLoader::blockingFetchTileRawData( mProvider.get(), mTileMatrixSet, viewCenter, it.value(), it.key(), &multiStepFeedback, Qgis::RendererUsage::Export );
    for ( const QgsVectorTileRawData &rawTile : std::as_const( rawTiles ) )
    {
      if ( feedback->isCanceled() )
        break;
 
      // TODO: at the moment, it handles single source only of tiles
      // takes the first one
      const QByteArray data = rawTile.data.first();
 
      if ( !data.isEmpty() )
      {
        QByteArray gzipTileData;
        QgsZipUtils::encodeGzip( data, gzipTileData );
        int rowTMS = pow( 2, rawTile.id.zoomLevel() ) - rawTile.id.row() - 1;
        writer->setTileData( rawTile.id.zoomLevel(), rawTile.id.column(), rowTMS, gzipTileData );
      }
 
      multiStepFeedback.setProgress( 100.0 * ( tileNumber++ ) / tileCount );
    }
 
    ++it;
  }
 
  if ( context.willLoadLayerOnCompletion( outputFile ) )
  {
    context.layerToLoadOnCompletionDetails( outputFile ).setPostProcessor( new SetStylePostProcessor( mStyleDocument ) );
  }
 
  QVariantMap results;
  results.insert( u"OUTPUT"_s, outputFile );
  return results;
}