qgsalgorithmxyztiles.cpp

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/***************************************************************************
                         qgsalgorithmxyztiles.cpp
                         ---------------------
    begin                : August 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 "qgsalgorithmxyztiles.h"
 
#include <algorithm>
#include <atomic>
 
#include "qgsexpressioncontextutils.h"
#include "qgsimageoperation.h"
#include "qgslayertree.h"
#include "qgslayertreelayer.h"
#include "qgsmaplayerutils.h"
#include "qgsprocessingparametertileextentmaxzoomlist.h"
#include "qgstiles.h"
 
#include <QBuffer>
#include <QDir>
#include <QQueue>
#include <QSemaphore>
#include <QSet>
#include <QString>
#include <QThread>
#include <QThreadPool>
#include <QWaitCondition>
 
using namespace Qt::StringLiterals;

 
 
namespace
{
  int tile2tms( const int y, const int zoom )
  {
    double n = std::pow( 2, zoom );
    return ( int ) std::floor( n - y - 1 );
  }
} //namespace
 
void MetaTile::addTile( const int row, const int col, Tile tileToAdd, const QgsRectangle &extent )
{
  tiles.insert( QPair<int, int>( row, col ), tileToAdd );
  if ( row >= rows )
  {
    rows = row + 1;
  }
  if ( col >= cols )
  {
    cols = col + 1;
  }
  mExtent.combineExtentWith( extent );
}
 
 
namespace
{
  QList<MetaTile> getMetatiles(
    const QgsTileMatrix &z0Matrix, const QgsRectangle &contentsExtent, int zoom, long long &tileCount, int metaTileSize, const QList<QgsTileExtentMaxZoomRegion> &maxZoomRegions, int defaultMaxZoom
  )
  {
    const QgsTileMatrix targetZoomMatrix = QgsTileMatrix::fromTileMatrix( zoom, z0Matrix );
 
    const long long matrixWidth = targetZoomMatrix.matrixWidth();
    const long long matrixHeight = targetZoomMatrix.matrixHeight();
 
    const QgsRectangle tileMatrixSetExtent = targetZoomMatrix.extent();
    const double tileWidthUnits = tileMatrixSetExtent.width() / matrixWidth;
    const double tileHeightUnits = tileMatrixSetExtent.height() / matrixHeight;
 
    int minX = static_cast<int>( std::floor( ( contentsExtent.xMinimum() - tileMatrixSetExtent.xMinimum() ) / tileWidthUnits ) );
    int maxX = static_cast<int>( std::ceil( ( contentsExtent.xMaximum() - tileMatrixSetExtent.xMinimum() ) / tileWidthUnits ) - 1 );
    int minY = static_cast<int>( std::floor( ( tileMatrixSetExtent.yMaximum() - contentsExtent.yMaximum() ) / tileHeightUnits ) );
    int maxY = static_cast<int>( std::ceil( ( tileMatrixSetExtent.yMaximum() - contentsExtent.yMinimum() ) / tileHeightUnits ) - 1 );
 
    minX = std::clamp<int>( minX, 0, static_cast<int>( matrixWidth - 1 ) );
    maxX = std::clamp<int>( maxX, 0, static_cast<int>( matrixWidth - 1 ) );
    minY = std::clamp<int>( minY, 0, static_cast<int>( matrixHeight - 1 ) );
    maxY = std::clamp<int>( maxY, 0, static_cast<int>( matrixHeight - 1 ) );
 
    // IMPORTANT - we have to snap the target extent out to multiples of the metatile!
    const int totalMetaColumns = static_cast<int>( std::ceil( static_cast<double>( maxX - minX + 1 ) / metaTileSize ) );
    const int totalMetaRows = static_cast<int>( std::ceil( static_cast<double>( maxY - minY + 1 ) / metaTileSize ) );
    tileCount = 0;
    QList<MetaTile> metaTiles;
    for ( int metaTileColumn = 0; metaTileColumn < totalMetaColumns; ++metaTileColumn )
    {
      const int startI = metaTileColumn * metaTileSize;
      const int endI = std::min( startI + metaTileSize - 1, maxX - minX );
      const int startX = minX + startI;
      const int endX = minX + endI;
 
      for ( int metaTileRow = 0; metaTileRow < totalMetaRows; ++metaTileRow )
      {
        const int startJ = metaTileRow * metaTileSize;
        const int endJ = std::min( startJ + metaTileSize - 1, maxY - minY );
        const int startY = minY + startJ;
        const int endY = minY + endJ;
 
        const double metaTileMinX = tileMatrixSetExtent.xMinimum() + startX * tileWidthUnits;
        const double metaTileMaxX = tileMatrixSetExtent.xMinimum() + ( endX + 1 ) * tileWidthUnits;
        const double metaTileMaxY = tileMatrixSetExtent.yMaximum() - startY * tileHeightUnits;
        const double metaTileMinY = tileMatrixSetExtent.yMaximum() - ( endY + 1 ) * tileHeightUnits;
        const QgsRectangle metaTileExtent( metaTileMinX, metaTileMaxY, metaTileMaxX, metaTileMinY );
 
        // check if there's any zoom overrides in place for this metatile
        if ( !maxZoomRegions.isEmpty() )
        {
          const int metaTileMaxZoom = QgsProcessingParameterTileExtentMaxZoomList::maxZoomForTile( metaTileExtent, maxZoomRegions, defaultMaxZoom );
 
          if ( metaTileMaxZoom < zoom )
          {
            // don't need this zoom level for this metatile
            continue;
          }
        }
 
        // build the actual metatile
        MetaTile metaTile;
        for ( int x = startX, i = startI; x <= endX; ++x, ++i )
        {
          for ( int y = startY, j = startJ; y <= endY; ++y, ++j )
          {
            const double tileMinX = tileMatrixSetExtent.xMinimum() + x * tileWidthUnits;
            const double tileMaxX = tileMinX + tileWidthUnits;
            const double tileMaxY = tileMatrixSetExtent.yMaximum() - y * tileHeightUnits;
            const double tileMinY = tileMaxY - tileHeightUnits;
 
            const QgsRectangle tileExtent( tileMinX, tileMinY, tileMaxX, tileMaxY );
 
            metaTile.addTile( i % metaTileSize, j % metaTileSize, Tile( x, y, zoom ), tileExtent );
            tileCount++;
          }
        }
 
        if ( !metaTile.tiles.isEmpty() )
        {
          metaTiles.append( metaTile );
        }
      }
    }
 
    return metaTiles;
  }
} //namespace

template<typename T> class PendingTilesToWriteQueue
{
  public:
    void push( const QList<T> &tiles )
    {
      if ( tiles.isEmpty() )
        return;
 
      QMutexLocker locker( &mMutex );
      for ( const T &tile : tiles )
      {
        mQueue.enqueue( tile );
      }
      mNotEmpty.wakeOne();
    }

    bool popBatch( QList<T> &batch, int maxBatchSize, unsigned long timeoutMs = 500 )
    {
      QMutexLocker locker( &mMutex );
 
      // wait until there is at least one item or all rendering is finished
      while ( mQueue.isEmpty() && !mFinished )
      {
        mNotEmpty.wait( &mMutex );
      }
 
      if ( mQueue.isEmpty() )
        return false;
 
      // collect up to to maxBatchSize, unless we finish rendering or timeout before that happens
      while ( mQueue.size() < maxBatchSize && !mFinished )
      {
        if ( !mNotEmpty.wait( &mMutex, timeoutMs ) )
        {
          // timeout exceeded
          break;
        }
      }
 
      while ( !mQueue.isEmpty() && batch.size() < maxBatchSize )
      {
        batch.append( mQueue.dequeue() );
      }
      return true;
    }

    void setFinished()
    {
      QMutexLocker locker( &mMutex );
      mFinished = true;
      mNotEmpty.wakeAll();
    }
 
  private:
    QQueue<T> mQueue;
    mutable QMutex mMutex;
    QWaitCondition mNotEmpty;
    bool mFinished = false;
};
 
//
// QgsXyzTilesBaseAlgorithm
//
 
QString QgsXyzTilesBaseAlgorithm::group() const
{
  return QObject::tr( "Raster tools" );
}
 
QString QgsXyzTilesBaseAlgorithm::groupId() const
{
  return u"rastertools"_s;
}
 
Qgis::ProcessingAlgorithmFlags QgsXyzTilesBaseAlgorithm::flags() const
{
  return QgsProcessingAlgorithm::flags() | Qgis::ProcessingAlgorithmFlag::RequiresProject;
}
 
void QgsXyzTilesBaseAlgorithm::createCommonParameters()
{
  auto extentParam = std::make_unique<QgsProcessingParameterExtent>( u"EXTENT"_s, QObject::tr( "Extent" ) );
  extentParam->setHelp( QObject::tr( "Spatial extent of the area for tile generation." ) );
  addParameter( extentParam.release() );
 
  auto minZoomParam = std::make_unique<QgsProcessingParameterNumber>( u"ZOOM_MIN"_s, QObject::tr( "Minimum zoom" ), Qgis::ProcessingNumberParameterType::Integer, 12, false, 0, 25 );
  minZoomParam->setHelp(
    QObject::tr(
      "Minimum zoom level for generated tiles (0–25). Lower zoom levels cover broader geographic areas "
      "at lower spatial resolution. Must be less than or equal to the maximum zoom level."
    )
  );
  addParameter( minZoomParam.release() );
 
  auto maxZoomParam = std::make_unique<QgsProcessingParameterNumber>( u"ZOOM_MAX"_s, QObject::tr( "Maximum zoom" ), Qgis::ProcessingNumberParameterType::Integer, 12, false, 0, 25 );
  maxZoomParam->setHelp(
    QObject::tr(
      "Maximum zoom level for generated tiles (0–25). Higher zoom levels capture finer map details "
      "and higher resolution, but exponentially increase total tile count, storage requirements, and rendering time. "
      "Must be greater than or equal to the minimum zoom level."
    )
  );
  addParameter( maxZoomParam.release() );
 
  auto dpiParam = std::make_unique<QgsProcessingParameterNumber>( u"DPI"_s, QObject::tr( "DPI" ), Qgis::ProcessingNumberParameterType::Integer, 96, false, 48, 600 );
  dpiParam->setHelp( QObject::tr( "Output resolution in DPI for rendered map content." ) );
  dpiParam->setFlags( dpiParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( dpiParam.release() );
 
  auto bgColorParam = std::make_unique<QgsProcessingParameterColor>( u"BACKGROUND_COLOR"_s, QObject::tr( "Background color" ), QColor( Qt::transparent ), true, true );
  bgColorParam->setHelp( QObject::tr( "Background color used when rendering map tiles." ) );
  addParameter( bgColorParam.release() );
 
  auto antialiasParam = std::make_unique<QgsProcessingParameterBoolean>( u"ANTIALIAS"_s, QObject::tr( "Enable antialiasing" ), true );
  antialiasParam->setHelp( QObject::tr( "Controls whether antialiasing is applied during tile rendering." ) );
  antialiasParam->setFlags( antialiasParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( antialiasParam.release() );
 
  auto tileFormatParam = std::make_unique<QgsProcessingParameterEnum>( u"TILE_FORMAT"_s, QObject::tr( "Tile format" ), QStringList { u"PNG"_s, u"JPG"_s, u"WEBP"_s }, false, 0 );
  tileFormatParam->setHelp( QObject::tr( "Output image format for the rendered tiles." ) );
  addParameter( tileFormatParam.release() );
 
  auto qualityParam = std::make_unique<QgsProcessingParameterNumber>( u"QUALITY"_s, QObject::tr( "Quality (JPG only)" ), Qgis::ProcessingNumberParameterType::Integer, 75, false, 1, 100 );
  qualityParam->setHelp( QObject::tr( "Image quality percentage used when tile format is set to JPG (1–100)." ) );
  qualityParam->setFlags( qualityParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( qualityParam.release() );
 
  auto metaTileSizeParam = std::make_unique<QgsProcessingParameterNumber>( u"METATILESIZE"_s, QObject::tr( "Metatile size" ), Qgis::ProcessingNumberParameterType::Integer, 4, false, 1, 20 );
  metaTileSizeParam->setHelp( QObject::tr( "Size of metatiles (in tile units) used during rendering." ) );
  metaTileSizeParam->setFlags( metaTileSizeParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( metaTileSizeParam.release() );
 
  auto skipEmptyTilesParam = std::make_unique<QgsProcessingParameterBoolean>( u"SKIP_EMPTY_TILES"_s, QObject::tr( "Skip empty tiles" ), false );
  skipEmptyTilesParam->setHelp( QObject::tr( "If set, completely empty tiles will be skipped." ) );
  skipEmptyTilesParam->setFlags( skipEmptyTilesParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( skipEmptyTilesParam.release() );
 
  auto tileExtentMaxZoomParam = std::make_unique<QgsProcessingParameterTileExtentMaxZoomList>( u"TILE_MAX_ZOOM_EXTENTS"_s, QObject::tr( "Maximum zoom extents" ), QVariant(), true );
  tileExtentMaxZoomParam->setHelp( QObject::tr( "Allows overriding the maximum zoom level for specific geographic regions, so that more detailed tiles can be created for important areas." ) );
  tileExtentMaxZoomParam->setFlags( tileExtentMaxZoomParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  addParameter( tileExtentMaxZoomParam.release() );
}
 
void QgsXyzTilesBaseAlgorithm::createTileMatrixParameters()
{
  auto crsParam = std::make_unique<QgsProcessingParameterCrs>( u"TARGET_CRS"_s, QObject::tr( "Target CRS" ), QVariant( u"EPSG:3857"_s ) );
  crsParam->setFlags( crsParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  crsParam->setHelp( QObject::tr( "Coordinate reference system used for the output tile matrix set." ) );
  addParameter( crsParam.release() );
 
  auto z0ExtentParam = std::make_unique<QgsProcessingParameterExtent>( u"Z0_EXTENT"_s, QObject::tr( "Zoom 0 extent" ) );
  z0ExtentParam->setFlags( z0ExtentParam->flags() | Qgis::ProcessingParameterFlag::Advanced | Qgis::ProcessingParameterFlag::Optional );
  z0ExtentParam->setHelp(
    QObject::tr(
      "Extent of zoom level 0 in target CRS coordinates. Required when target CRS is not EPSG:3857. If the target CRS is EPSG:3857 then this parameter will be ignored and a standard Web Mercator "
      "tile matrix will be used instead."
    )
  );
  addParameter( z0ExtentParam.release() );
 
  auto z0WidthParam = std::make_unique<QgsProcessingParameterNumber>( u"Z0_MATRIX_WIDTH"_s, QObject::tr( "Zoom 0 matrix width" ), Qgis::ProcessingNumberParameterType::Integer, 1, false, 1 );
  z0WidthParam->setFlags( z0WidthParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  z0WidthParam->setHelp( QObject::tr( "Number of tile columns at zoom level 0 (matrix width)." ) );
  addParameter( z0WidthParam.release() );
 
  auto z0HeightParam = std::make_unique<QgsProcessingParameterNumber>( u"Z0_MATRIX_HEIGHT"_s, QObject::tr( "Zoom 0 matrix height" ), Qgis::ProcessingNumberParameterType::Integer, 1, false, 1 );
  z0HeightParam->setFlags( z0HeightParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  z0HeightParam->setHelp( QObject::tr( "Number of tile rows at zoom level 0 (matrix height)." ) );
  addParameter( z0HeightParam.release() );
}
 
bool QgsXyzTilesBaseAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  Q_UNUSED( feedback );
 
  QgsProject *project = context.project();
 
  mExpressionContext = context.expressionContext();
 
  const QList<QgsLayerTreeLayer *> projectLayers = project->layerTreeRoot()->findLayers();
  QSet<QString> visibleLayers;
  for ( const QgsLayerTreeLayer *layer : projectLayers )
  {
    if ( layer->isVisible() )
    {
      visibleLayers << layer->layer()->id();
    }
  }
 
  const QList<QgsMapLayer *> renderLayers = project->layerTreeRoot()->layerOrder();
  for ( QgsMapLayer *layer : renderLayers )
  {
    if ( visibleLayers.contains( layer->id() ) )
    {
      QgsMapLayer *clonedLayer = layer->clone();
      clonedLayer->moveToThread( nullptr );
      mLayers << clonedLayer;
    }
  }
 
  if ( parameters.contains( u"TILE_WIDTH"_s ) )
  {
    mTileWidth = parameterAsInt( parameters, u"TILE_WIDTH"_s, context );
  }
 
  if ( parameters.contains( u"TILE_HEIGHT"_s ) )
  {
    mTileHeight = parameterAsInt( parameters, u"TILE_HEIGHT"_s, context );
  }
 
  if ( parameters.contains( u"TARGET_CRS"_s ) )
  {
    mTargetCrs = parameterAsCrs( parameters, u"TARGET_CRS"_s, context );
  }
  else
  {
    mTargetCrs = QgsCoordinateReferenceSystem( u"EPSG:3857"_s );
  }
 
  int z0MatrixWidth = 1;
  if ( parameters.contains( u"Z0_MATRIX_WIDTH"_s ) )
  {
    z0MatrixWidth = parameterAsInt( parameters, u"Z0_MATRIX_WIDTH"_s, context );
  }
 
  int z0MatrixHeight = 1;
  if ( parameters.contains( u"Z0_MATRIX_HEIGHT"_s ) )
  {
    z0MatrixHeight = parameterAsInt( parameters, u"Z0_MATRIX_HEIGHT"_s, context );
  }
 
  mTileGenerationRegion = parameterAsExtent( parameters, u"EXTENT"_s, context, mTargetCrs );
 
  const QgsRectangle userZ0Extent = parameterAsExtent( parameters, u"Z0_EXTENT"_s, context, mTargetCrs );
  QgsRectangle z0Extent;
  if ( mTargetCrs.authid() == "EPSG:3857"_L1 )
  {
    if ( !userZ0Extent.isEmpty() )
    {
      feedback->pushWarning( QObject::tr( "Tiles are being generated in EPSG:3857, so a standard Web Mercator tile matrix will be used. The manual zoom 0 extent will be ignored." ) );
    }
    z0Extent = QgsRectangle( -MERC_MAX, -MERC_MAX, MERC_MAX, MERC_MAX );
  }
  else
  {
    if ( userZ0Extent.isEmpty() )
    {
      throw QgsProcessingException( QObject::tr( "Zoom 0 extent must be specified when using a custom target CRS (%1)" ).arg( mTargetCrs.userFriendlyIdentifier() ) );
    }
    z0Extent = userZ0Extent;
    const double rawPixelXSize = z0Extent.width() / ( static_cast<double>( z0MatrixWidth ) * mTileWidth );
    const double rawPixelYSize = z0Extent.height() / ( static_cast<double>( z0MatrixHeight ) * mTileHeight );
 
    // tile matrix extents MUST be square! Expanding the tile matrix set extent around its center to force this.
    if ( !qgsDoubleNear( rawPixelXSize, rawPixelYSize, 1e-9 ) )
    {
      const double isotropicPixelSize = std::max( rawPixelXSize, rawPixelYSize );
      const double requiredWidth = isotropicPixelSize * z0MatrixWidth * mTileWidth;
      const double requiredHeight = isotropicPixelSize * z0MatrixHeight * mTileHeight;
 
      const QgsPointXY center = z0Extent.center();
      z0Extent = QgsRectangle( center.x() - requiredWidth / 2.0, center.y() - requiredHeight / 2.0, center.x() + requiredWidth / 2.0, center.y() + requiredHeight / 2.0 );
    }
  }
 
  mZ0matrix = QgsTileMatrix::fromCustomDef( 0, mTargetCrs, QgsPointXY( z0Extent.xMinimum(), z0Extent.yMaximum() ), z0Extent.width() / z0MatrixWidth, z0MatrixWidth, z0MatrixHeight );
 
  QgsCoordinateTransform src2Wgs = QgsCoordinateTransform( mTargetCrs, QgsCoordinateReferenceSystem( u"EPSG:4326"_s ), context.transformContext() );
  src2Wgs.setBallparkTransformsAreAppropriate( true );
  try
  {
    mWgs84Extent = src2Wgs.transformBoundingBox( mTileGenerationRegion );
  }
  catch ( QgsCsException & )
  {
    throw QgsProcessingException( QObject::tr( "Could not transform the extent into WGS84" ) );
  }
 
  mMinZoom = parameterAsInt( parameters, u"ZOOM_MIN"_s, context );
  mMaxZoom = parameterAsInt( parameters, u"ZOOM_MAX"_s, context );
  if ( mMaxZoom < mMinZoom )
  {
    throw QgsProcessingException( QObject::tr( "Maximum zoom (%1) must be ≥ minimum zoom (%2)" ).arg( mMaxZoom ).arg( mMinZoom ) );
  }
 
  mMaxZoomLimitIncludingOverrides = mMaxZoom;
  const QList<QgsTileExtentMaxZoomRegion> rawRegions
    = qgis::down_cast< const QgsProcessingParameterTileExtentMaxZoomList *>( parameterDefinition( u"TILE_MAX_ZOOM_EXTENTS"_s ) )->parameterAsRegionList( parameters.value( u"TILE_MAX_ZOOM_EXTENTS"_s ), context );
  if ( !rawRegions.isEmpty() )
  {
    // convert all override regions to target crs once in advance
    for ( const QgsTileExtentMaxZoomRegion &region : rawRegions )
    {
      QgsTileExtentMaxZoomRegion targetRegion = region;
      try
      {
        QgsCoordinateTransform ct( region.extent.crs(), mTargetCrs, context.transformContext() );
        ct.setBallparkTransformsAreAppropriate( true );
        targetRegion.extent = QgsReferencedRectangle( ct.transformBoundingBox( region.extent ), mTargetCrs );
        mMaxZoomRegions.append( targetRegion );
        mMaxZoomLimitIncludingOverrides = std::max( mMaxZoomLimitIncludingOverrides, region.maxZoom );
      }
      catch ( QgsCsException & )
      {
        continue;
      }
    }
  }
 
  mDpi = parameterAsInt( parameters, u"DPI"_s, context );
  mBackgroundColor = parameterAsColor( parameters, u"BACKGROUND_COLOR"_s, context );
  mAntialias = parameterAsBool( parameters, u"ANTIALIAS"_s, context );
  mSkipEmptyTiles = parameterAsBool( parameters, u"SKIP_EMPTY_TILES"_s, context );
  switch ( parameterAsEnum( parameters, u"TILE_FORMAT"_s, context ) )
  {
    case 0:
      mTileFormat = u"PNG"_s;
      break;
    case 1:
      mTileFormat = u"JPG"_s;
      break;
    case 2:
      mTileFormat = u"WEBP"_s;
      break;
    default:
      mTileFormat = u"PNG"_s;
      break;
  }
 
  mJpgQuality = mTileFormat != "PNG"_L1 ? parameterAsInt( parameters, u"QUALITY"_s, context ) : -1;
  mMetaTileSize = parameterAsInt( parameters, u"METATILESIZE"_s, context );
  mThreadsNumber = context.maximumThreads();
  mTransformContext = context.transformContext();
  mEllipsoid = context.ellipsoid();
 
  if ( ( mTileFormat != "PNG"_L1 && mTileFormat != "WEBP"_L1 ) && mBackgroundColor.alpha() != 255 )
  {
    feedback->pushWarning(
      QObject::tr( "A semi-transparent background color was set, but the JPG format only supports fully opaque colors. The background color setting will be ignored. Please use a fully opaque background color instead." )
    );
  }
 
  mScaleMethod = project->scaleMethod();
 
  return true;
}
 
void QgsXyzTilesBaseAlgorithm::checkLayersUsagePolicy( QgsProcessingFeedback *feedback )
{
  if ( mTotalMetaTiles > MAXIMUM_OPENSTREETMAP_TILES_FETCH )
  {
    for ( QgsMapLayer *layer : std::as_const( mLayers ) )
    {
      if ( QgsMapLayerUtils::isOpenStreetMapLayer( layer ) )
      {
        // Prevent bulk downloading of tiles from openstreetmap.org as per OSMF tile usage policy
        feedback->pushFormattedMessage(
          QObject::tr( "Layer %1 will be skipped as the algorithm leads to bulk downloading behavior which is prohibited by the %2OpenStreetMap Foundation tile usage policy%3" )
            .arg( layer->name(), u"<a href=\"https://operations.osmfoundation.org/policies/tiles/\">"_s, u"</a>"_s ),
          QObject::tr( "Layer %1 will be skipped as the algorithm leads to bulk downloading behavior which is prohibited by the %2OpenStreetMap Foundation tile usage policy%3" )
            .arg( layer->name(), QString(), QString() )
        );
        mLayers.removeAll( layer );
        delete layer;
      }
    }
  }
}
 
std::optional< QgsMapSettings > QgsXyzTilesBaseAlgorithm::mapSettingsForTile( const MetaTile &metaTile ) const
{
  QgsMapSettings settings;
  settings.setExtent( metaTile.mExtent );
  settings.setDestinationCrs( mTargetCrs );
  settings.setRendererUsage( Qgis::RendererUsage::Export );
  settings.setOutputImageFormat( QImage::Format_ARGB32_Premultiplied );
  settings.setTransformContext( mTransformContext );
  settings.setEllipsoid( mEllipsoid );
  settings.setLayers( mLayers );
  settings.setOutputDpi( mDpi );
  settings.setFlag( Qgis::MapSettingsFlag::Antialiasing, mAntialias );
  settings.setFlag( Qgis::MapSettingsFlag::RenderMapTile, true );
  settings.setFlag( Qgis::MapSettingsFlag::UseRenderingOptimization, true );
  settings.setFlag( Qgis::MapSettingsFlag::HighQualityImageTransforms, true );
  settings.setRasterizedRenderingPolicy( Qgis::RasterizedRenderingPolicy::Default );
  settings.setScaleMethod( mScaleMethod );
  if ( mTileFormat == "PNG"_L1 || mTileFormat == "WEBP"_L1 || mBackgroundColor.alpha() == 255 )
  {
    settings.setBackgroundColor( mBackgroundColor );
  }
  QSize size( mTileWidth * metaTile.rows, mTileHeight * metaTile.cols );
  settings.setOutputSize( size );
 
  QgsLabelingEngineSettings labelingSettings = settings.labelingEngineSettings();
  labelingSettings.setFlag( Qgis::LabelingFlag::UsePartialCandidates, false );
  settings.setLabelingEngineSettings( labelingSettings );
 
  QgsExpressionContext exprContext = mExpressionContext;
  exprContext.appendScope( QgsExpressionContextUtils::mapSettingsScope( settings ) );
  settings.setExpressionContext( exprContext );
 
  return settings;
}
 
void QgsXyzTilesBaseAlgorithm::startJobs( QgsProcessingFeedback *feedback )
{
  while ( mRendererJobs.size() < mThreadsNumber && !mMetaTiles.empty() )
  {
    if ( feedback->isCanceled() )
      break;
 
    MetaTile metaTile = mMetaTiles.takeFirst();
    const std::optional<QgsMapSettings> settings = mapSettingsForTile( metaTile );
    if ( !settings.has_value() )
    {
      mProcessedMetaTiles++;
      feedback->setProgress( 100.0 * mProcessedMetaTiles / mTotalMetaTiles );
      continue;
    }
 
    QgsMapRendererSequentialJob *job = new QgsMapRendererSequentialJob( *settings );
    mRendererJobs.insert( job, metaTile );
 
    QObject::connect( job, &QgsMapRendererJob::finished, mJobOwner, [this, feedback, job]() {
      const MetaTile tile = mRendererJobs.take( job );
      const QImage renderedImage = job->renderedImage();
      job->deleteLater();
 
      mProcessedMetaTiles++;
      feedback->setProgress( 100.0 * mProcessedMetaTiles / mTotalMetaTiles );
 
      processMetaTile( tile, renderedImage, feedback );
 
      if ( !feedback->isCanceled() )
      {
        startJobs( feedback );
      }
      checkPipelineFinished( feedback );
    } );
 
    job->start();
  }
 
  checkPipelineFinished( feedback );
}
 
void QgsXyzTilesBaseAlgorithm::checkPipelineFinished( QgsProcessingFeedback *feedback )
{
  if ( feedback->isCanceled() || ( mMetaTiles.isEmpty() && mRendererJobs.isEmpty() && mActivePostProcessingTasks == 0 ) )
  {
    if ( mEventLoop )
    {
      mEventLoop->exit();
    }
  }
}
 
//
// QgsXyzTilesDirectoryAlgorithm
//
 
QString QgsXyzTilesDirectoryAlgorithm::name() const
{
  return u"tilesxyzdirectory"_s;
}
 
QString QgsXyzTilesDirectoryAlgorithm::displayName() const
{
  return QObject::tr( "Generate XYZ tiles (Directory)" );
}
 
QStringList QgsXyzTilesDirectoryAlgorithm::tags() const
{
  return QObject::tr( "tiles,xyz,tms,directory" ).split( ',' );
}
 
QString QgsXyzTilesDirectoryAlgorithm::shortHelpString() const
{
  return QObject::tr(
    "This algorithm generates XYZ raster tiles from the current project and saves them as individual image files in a structured directory hierarchy ({z}/{x}/{y}.png or .jpg).\n\n"
    "All visible map layers from the project will be rendered into tiles across the specified extent and zoom range.\n\n"
    "Optionally, a standalone Leaflet HTML file can be generated for instant web previewing of the tiles."
  );
}
 
QString QgsXyzTilesDirectoryAlgorithm::shortDescription() const
{
  return QObject::tr( "Generates XYZ tiles from the project as a structured directory hierarchy ({z}/{x}/{y}.png/jpg)." );
}
 
QgsXyzTilesDirectoryAlgorithm *QgsXyzTilesDirectoryAlgorithm::createInstance() const
{
  return new QgsXyzTilesDirectoryAlgorithm();
}
 
void QgsXyzTilesDirectoryAlgorithm::initAlgorithm( const QVariantMap & )
{
  createCommonParameters();
  createTileMatrixParameters();
 
  auto tileWidthParam = std::make_unique<QgsProcessingParameterNumber>( u"TILE_WIDTH"_s, QObject::tr( "Tile width" ), Qgis::ProcessingNumberParameterType::Integer, 256, false, 1, 4096 );
  tileWidthParam->setHelp( QObject::tr( "Width of each tile image in pixels." ) );
  addParameter( tileWidthParam.release() );
 
  auto tileHeightParam = std::make_unique<QgsProcessingParameterNumber>( u"TILE_HEIGHT"_s, QObject::tr( "Tile height" ), Qgis::ProcessingNumberParameterType::Integer, 256, false, 1, 4096 );
  tileHeightParam->setHelp( QObject::tr( "Height of each tile image in pixels." ) );
  addParameter( tileHeightParam.release() );
 
  auto tmsParam = std::make_unique<QgsProcessingParameterBoolean>( u"TMS_CONVENTION"_s, QObject::tr( "Use inverted tile Y axis (TMS convention)" ), false );
  tmsParam->setHelp( QObject::tr( "Inverts the Y tile coordinate naming convention to follow TMS format." ) );
  addParameter( tmsParam.release() );
 
  auto titleParam = std::make_unique<QgsProcessingParameterString>( u"HTML_TITLE"_s, QObject::tr( "Leaflet HTML output title" ), QVariant(), false, true );
  titleParam->setFlags( titleParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  titleParam->setHelp( QObject::tr( "Title displayed in the generated Leaflet HTML web viewer." ) );
  addParameter( titleParam.release() );
 
  auto attributionParam = std::make_unique<QgsProcessingParameterString>( u"HTML_ATTRIBUTION"_s, QObject::tr( "Leaflet HTML output attribution" ), QVariant(), false, true );
  attributionParam->setFlags( attributionParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  attributionParam->setHelp( QObject::tr( "Attribution text displayed in the generated Leaflet HTML web viewer." ) );
  addParameter( attributionParam.release() );
 
  auto osmParam = std::make_unique<QgsProcessingParameterBoolean>( u"HTML_OSM"_s, QObject::tr( "Include OpenStreetMap basemap in Leaflet HTML output" ), false );
  osmParam->setFlags( osmParam->flags() | Qgis::ProcessingParameterFlag::Advanced );
  osmParam->setHelp( QObject::tr( "Includes an OpenStreetMap background layer in the generated Leaflet HTML viewer." ) );
  addParameter( osmParam.release() );
 
  auto outputDirParam = std::make_unique<QgsProcessingParameterFolderDestination>( u"OUTPUT_DIRECTORY"_s, QObject::tr( "Output directory" ) );
  outputDirParam->setHelp( QObject::tr( "Destination folder where the generated directory structure and tile files will be stored." ) );
  addParameter( outputDirParam.release() );
 
  auto outputHtmlParam = std::make_unique<QgsProcessingParameterFileDestination>( u"OUTPUT_HTML"_s, QObject::tr( "Output HTML (Leaflet)" ), QObject::tr( "HTML files (*.html)" ), QVariant(), true );
  outputHtmlParam->setHelp( QObject::tr( "Destination file path for the optional Leaflet HTML web map preview." ) );
  addParameter( outputHtmlParam.release() );
 
  addOutput( new QgsProcessingOutputRasterLayer( u"OUTPUT_LAYER"_s, QObject::tr( "Output tiles as raster layer" ) ) );
}
 
QVariantMap QgsXyzTilesDirectoryAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  QGS_MARK_ALGORITHM_SOURCE
 
  const bool tms = parameterAsBoolean( parameters, u"TMS_CONVENTION"_s, context );
  const QString title = parameterAsString( parameters, u"HTML_TITLE"_s, context );
  const QString attribution = parameterAsString( parameters, u"HTML_ATTRIBUTION"_s, context );
  const bool useOsm = parameterAsBoolean( parameters, u"HTML_OSM"_s, context );
  QString outputDir = parameterAsString( parameters, u"OUTPUT_DIRECTORY"_s, context );
  const QString outputHtml = parameterAsString( parameters, u"OUTPUT_HTML"_s, context );
 
  mOutputDir = outputDir;
  mTms = tms;
 
  long long totalTiles = 0;
  mTotalMetaTiles = 0;
  for ( int z = mMinZoom; z <= mMaxZoomLimitIncludingOverrides; z++ )
  {
    if ( feedback->isCanceled() )
      break;
 
    long long tileCount = 0;
    mMetaTiles += getMetatiles( mZ0matrix, mTileGenerationRegion, z, tileCount, mMetaTileSize, mMaxZoomRegions, mMaxZoom );
    feedback->pushInfo( QObject::tr( "%1 metatiles (%2 tiles) will be created for zoom level %3" ).arg( mMetaTiles.size() - mTotalMetaTiles ).arg( tileCount ).arg( z ) );
    mTotalMetaTiles = mMetaTiles.size();
    totalTiles += tileCount;
  }
  if ( mTotalMetaTiles == 0 )
  {
    throw QgsProcessingException( QObject::tr( "No metatiles will be created -- please check the extent and zoom limits" ) );
  }
 
  feedback->pushInfo( QObject::tr( "A total of %1 metatiles (%2 tiles) will be created" ).arg( mTotalMetaTiles ).arg( totalTiles ) );
 
  checkLayersUsagePolicy( feedback );
 
  for ( QgsMapLayer *layer : std::as_const( mLayers ) )
  {
    layer->moveToThread( QThread::currentThread() );
  }
 
  doExport( feedback );
 
  qDeleteAll( mLayers );
  mLayers.clear();
 
  if ( mSkipEmptyTiles )
  {
    feedback->pushInfo( QObject::tr( "Wrote %1 total tiles, skipped %2 empty tiles" ).arg( mTilesWritten.load() ).arg( mEmptyTiles.load() ) );
  }
 
  QVariantMap results;
  results.insert( u"OUTPUT_DIRECTORY"_s, outputDir );
 
  if ( !outputHtml.isEmpty() )
  {
    const QString osm = QStringLiteral(
                          "var osm_layer = L.tileLayer('https://tile.openstreetmap.org/{z}/{x}/{y}.png',"
                          "{minZoom: %1, maxZoom: %2, attribution: '&copy; <a href=\"https://www.openstreetmap.org/copyright\">OpenStreetMap</a> contributors'}).addTo(map);"
    )
                          .arg( mMinZoom )
                          .arg( mMaxZoomLimitIncludingOverrides );
 
    const QString addOsm = useOsm ? osm : QString();
    const QString tmsConvention = tms ? u"true"_s : u"false"_s;
    const QString attr = attribution.isEmpty() ? u"Created by QGIS"_s : attribution;
    const QString tileSource = u"'file:///%1/{z}/{x}/{y}.%2'"_s.arg( outputDir.replace( "\\", "/" ).toHtmlEscaped(), mTileFormat.toLower() );
 
    const QString html = QStringLiteral(
                           "<!DOCTYPE html><html><head><title>%1</title><meta charset=\"utf-8\"/>"
                           "<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">"
                           "<link rel=\"stylesheet\" href=\"https://unpkg.com/leaflet@1.9.4/dist/leaflet.css\""
                           "integrity=\"sha384-sHL9NAb7lN7rfvG5lfHpm643Xkcjzp4jFvuavGOndn6pjVqS6ny56CAt3nsEVT4H\""
                           "crossorigin=\"\"/>"
                           "<script src=\"https://unpkg.com/leaflet@1.9.4/dist/leaflet.js\""
                           "integrity=\"sha384-cxOPjt7s7Iz04uaHJceBmS+qpjv2JkIHNVcuOrM+YHwZOmJGBXI00mdUXEq65HTH\""
                           "crossorigin=\"\"></script>"
                           "<style type=\"text/css\">body {margin: 0;padding: 0;} html, body, #map{width: 100%;height: 100%;}</style></head>"
                           "<body><div id=\"map\"></div><script>"
                           "var map = L.map('map', {attributionControl: false}).setView([%2, %3], %4);"
                           "L.control.attribution({prefix: false}).addTo(map);"
                           "%5"
                           "var tilesource_layer = L.tileLayer(%6, {minZoom: %7, maxZoom: %8, tms: %9, attribution: '%10'}).addTo(map);"
                           "</script></body></html>"
    )
                           .arg( title.isEmpty() ? u"Leaflet preview"_s : title )
                           .arg( mWgs84Extent.center().y() )
                           .arg( mWgs84Extent.center().x() )
                           .arg( ( mMaxZoom + mMinZoom ) / 2 )
                           .arg( addOsm, tileSource )
                           .arg( mMinZoom )
                           .arg( mMaxZoomLimitIncludingOverrides )
                           .arg( tmsConvention, attr );
 
    QFile htmlFile( outputHtml );
    if ( !htmlFile.open( QIODevice::WriteOnly | QIODevice::Truncate ) )
    {
      throw QgsProcessingException( QObject::tr( "Could not open html file %1" ).arg( outputHtml ) );
    }
    QTextStream fout( &htmlFile );
    fout << html;
 
    results.insert( u"OUTPUT_HTML"_s, outputHtml );
  }
 
  // try to load the result as a raster layer
  if ( !feedback->isCanceled() )
  {
    const QString layerUri
      = u"type=xyz&url=file:///%1/%7Bz%7D/%7Bx%7D/%7By%7D.%2&zmax=%3&zmin=%4"_s.arg( outputDir.replace( "\\", "/" ).toHtmlEscaped(), mTileFormat.toLower() ).arg( mMaxZoom ).arg( mMinZoom );
    auto layer = std::make_unique<QgsRasterLayer>( layerUri, "OUTPUT_LAYER", u"wms"_s );
    if ( !layer->isValid() )
    {
      feedback->reportError( QObject::tr( "Failed to open XYZ directory as a raster layer" ) );
    }
    const QString layerId = layer->id();
    const QgsProcessingContext::LayerDetails details( layer->name(), context.project(), u"OUTPUT_LAYER"_s, QgsProcessingUtils::LayerHint::Raster );
    details.setOutputLayerName( layer.get() );
    context.addLayerToLoadOnCompletion( layerId, details );
    context.temporaryLayerStore()->addMapLayer( layer.release() );
    results.insert( u"OUTPUT_LAYER"_s, layerId );
  }
 
  return results;
}
 
void QgsXyzTilesDirectoryAlgorithm::processMetaTile( const MetaTile &metaTile, const QImage &renderedImage, QgsProcessingFeedback *feedback )
{
  mActivePostProcessingTasks++;
 
  mPostProcessingPool->start( [this, metaTile, renderedImage, feedback]() {
    const bool testEmptyTilesUsingAlpha0 = mTileFormat != "JPG"_L1 && mBackgroundColor.alpha() == 0;
    long long localWritten = 0;
    long long localEmpty = 0;
 
    QSet<QString> createdDirs;
 
    for ( auto it = metaTile.tiles.constBegin(); it != metaTile.tiles.constEnd(); ++it )
    {
      if ( feedback->isCanceled() )
        break;
 
      const QPair<int, int> tm = it.key();
      const QImage tileImage = renderedImage.copy( mTileWidth * tm.first, mTileHeight * tm.second, mTileWidth, mTileHeight );
      const bool skipTile = mSkipEmptyTiles && ( testEmptyTilesUsingAlpha0 ? QgsImageOperation::isBlankImage( tileImage ) : QgsImageOperation::isSingleColor( tileImage, mBackgroundColor ) );
      if ( skipTile )
      {
        localEmpty++;
        continue;
      }
 
      const Tile tile = it.value();
      const QString dirPath = u"%1/%2/%3"_s.arg( mOutputDir ).arg( tile.z ).arg( tile.x );
      if ( !createdDirs.contains( dirPath ) )
      {
        QDir().mkpath( dirPath );
        createdDirs.insert( dirPath );
      }
 
      const int y = mTms ? tile2tms( tile.y, tile.z ) : tile.y;
      const QString filePath = u"%1/%2.%3"_s.arg( dirPath ).arg( y ).arg( mTileFormat.toLower() );
      tileImage.save( filePath, mTileFormat.toStdString().c_str(), mJpgQuality );
 
      localWritten++;
    }
 
    mTilesWritten += localWritten;
    mEmptyTiles += localEmpty;
 
    mActivePostProcessingTasks--;
    checkPipelineFinished( feedback );
  } );
}
 
void QgsXyzTilesDirectoryAlgorithm::doExport( QgsProcessingFeedback *feedback )
{
  mPostProcessingPool = std::make_unique<QThreadPool>();
  mPostProcessingPool->setMaxThreadCount( std::max( 1, mThreadsNumber ) );
 
  QEventLoop loop;
  mEventLoop = &loop;
  mJobOwner.reset( new QObject() );
 
  startJobs( feedback );
 
  if ( !mMetaTiles.isEmpty() || !mRendererJobs.isEmpty() || mActivePostProcessingTasks.load() > 0 )
  {
    loop.exec();
  }
 
  for ( auto it = mRendererJobs.constBegin(); it != mRendererJobs.constEnd(); it++ )
  {
    it.key()->cancel();
    it.key()->deleteLater();
  }
  mRendererJobs.clear();
 
  mPostProcessingPool->waitForDone();
  mPostProcessingPool.reset();
  mEventLoop = nullptr;
}
 
 
//
// QgsXyzTilesMbtilesAlgorithm
//
 
QString QgsXyzTilesMbtilesAlgorithm::name() const
{
  return u"tilesxyzmbtiles"_s;
}
 
QString QgsXyzTilesMbtilesAlgorithm::displayName() const
{
  return QObject::tr( "Generate XYZ tiles (MBTiles)" );
}
 
QStringList QgsXyzTilesMbtilesAlgorithm::tags() const
{
  return QObject::tr( "tiles,xyz,tms,mbtiles" ).split( ',' );
}
 
QString QgsXyzTilesMbtilesAlgorithm::shortHelpString() const
{
  return QObject::tr(
    "This algorithm generates XYZ raster tiles from the current project and packages them into a single, portable MBTiles (SQLite) database file.\n\n"
    "All visible map layers from the project will be rendered into tiles across the specified extent and zoom range."
  );
}
 
QString QgsXyzTilesMbtilesAlgorithm::shortDescription() const
{
  return QObject::tr( "Generates XYZ tiles from the project as a single, portable MBTiles (SQLite) database." );
}
 
QgsXyzTilesMbtilesAlgorithm *QgsXyzTilesMbtilesAlgorithm::createInstance() const
{
  return new QgsXyzTilesMbtilesAlgorithm();
}
 
void QgsXyzTilesMbtilesAlgorithm::initAlgorithm( const QVariantMap & )
{
  createCommonParameters();
  addParameter( new QgsProcessingParameterFileDestination( u"OUTPUT_FILE"_s, QObject::tr( "Output" ), QObject::tr( "MBTiles files (*.mbtiles *.MBTILES)" ) ) );
 
  addOutput( new QgsProcessingOutputRasterLayer( u"OUTPUT_LAYER"_s, QObject::tr( "Output MBTiles raster layer" ) ) );
}
 
QVariantMap QgsXyzTilesMbtilesAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  QGS_MARK_ALGORITHM_SOURCE
 
  const QString outputFile = parameterAsString( parameters, u"OUTPUT_FILE"_s, context );
  if ( QFile::exists( outputFile ) )
  {
    feedback->pushWarning( QObject::tr( "Removing existing file '%1'" ).arg( QDir::toNativeSeparators( outputFile ) ) );
    if ( !QFile( outputFile ).remove() )
    {
      throw QgsProcessingException( QObject::tr( "Could not remove existing file '%1'" ).arg( QDir::toNativeSeparators( outputFile ) ) );
    }
  }
 
  mMbtilesWriter = std::make_unique<QgsMbTiles>( outputFile );
  // use deferred index creation, as we'll be writing 1000s of tiles and don't want to update
  // the index after every one
  if ( !mMbtilesWriter->create( true ) )
  {
    throw QgsProcessingException( QObject::tr( "Failed to create MBTiles file %1: %2" ).arg( outputFile, mMbtilesWriter->lastError() ) );
  }
  mMbtilesWriter->setMetadataValue( u"format"_s, mTileFormat.toLower() );
  mMbtilesWriter->setMetadataValue( u"name"_s, QFileInfo( outputFile ).baseName() );
  mMbtilesWriter->setMetadataValue( u"description"_s, QFileInfo( outputFile ).baseName() );
  mMbtilesWriter->setMetadataValue( u"version"_s, u"1.1"_s );
  mMbtilesWriter->setMetadataValue( u"type"_s, u"overlay"_s );
  mMbtilesWriter->setMetadataValue( u"minzoom"_s, QString::number( mMinZoom ) );
  mMbtilesWriter->setMetadataValue( u"maxzoom"_s, QString::number( mMaxZoomLimitIncludingOverrides ) );
  QString boundsStr = QString( u"%1,%2,%3,%4"_s ).arg( mWgs84Extent.xMinimum() ).arg( mWgs84Extent.yMinimum() ).arg( mWgs84Extent.xMaximum() ).arg( mWgs84Extent.yMaximum() );
  mMbtilesWriter->setMetadataValue( u"bounds"_s, boundsStr );
 
  long long totalTiles = 0;
  mTotalMetaTiles = 0;
  for ( int z = mMinZoom; z <= mMaxZoomLimitIncludingOverrides; z++ )
  {
    if ( feedback->isCanceled() )
      break;
 
    long long tileCount = 0;
    mMetaTiles += getMetatiles( mZ0matrix, mTileGenerationRegion, z, tileCount, mMetaTileSize, mMaxZoomRegions, mMaxZoom );
    feedback->pushInfo( QObject::tr( "%1 metatiles (%2 tiles) will be created for zoom level %3" ).arg( mMetaTiles.size() - mTotalMetaTiles ).arg( tileCount ).arg( z ) );
    mTotalMetaTiles = mMetaTiles.size();
    totalTiles += tileCount;
  }
  if ( mTotalMetaTiles == 0 )
  {
    throw QgsProcessingException( QObject::tr( "No metatiles will be created -- please check the extent and zoom limits" ) );
  }
 
  feedback->pushInfo( QObject::tr( "A total of %1 metatiles (%2 tiles) will be created" ).arg( mTotalMetaTiles ).arg( totalTiles ) );
 
  checkLayersUsagePolicy( feedback );
 
  for ( QgsMapLayer *layer : std::as_const( mLayers ) )
  {
    layer->moveToThread( QThread::currentThread() );
  }
 
  doExport( feedback );
 
  qDeleteAll( mLayers );
  mLayers.clear();
 
  if ( !feedback->isCanceled() )
  {
    mMbtilesWriter->finalize();
  }
 
  if ( mSkipEmptyTiles )
  {
    feedback->pushInfo( QObject::tr( "Wrote %1 total tiles, skipped %2 empty tiles" ).arg( mTilesWritten.load() ).arg( mEmptyTiles.load() ) );
  }
  QVariantMap results;
  results.insert( u"OUTPUT_FILE"_s, outputFile );
 
  // try to load the result as a raster layer
  if ( !feedback->isCanceled() )
  {
    auto layer = std::make_unique<QgsRasterLayer>( outputFile, "OUTPUT_LAYER", u"gdal"_s );
    if ( !layer->isValid() )
    {
      feedback->reportError( QObject::tr( "Failed to open MBTiles file as a raster layer" ) );
    }
    const QString layerId = layer->id();
    const QgsProcessingContext::LayerDetails details( layer->name(), context.project(), u"OUTPUT_LAYER"_s, QgsProcessingUtils::LayerHint::Raster );
    details.setOutputLayerName( layer.get() );
    context.addLayerToLoadOnCompletion( layerId, details );
    context.temporaryLayerStore()->addMapLayer( layer.release() );
    results.insert( u"OUTPUT_LAYER"_s, layerId );
  }
 
  return results;
}
 
void QgsXyzTilesMbtilesAlgorithm::processMetaTile( const MetaTile &metaTile, const QImage &renderedImg, QgsProcessingFeedback *feedback )
{
  mActivePostProcessingTasks++;
 
  mPostProcessingPool->start( [this, feedback, metaTile, renderedImg]() {
    const bool testEmptyTilesUsingAlpha0 = mTileFormat != "JPG"_L1 && mBackgroundColor.alpha() == 0;
    long long localWritten = 0;
    long long localEmpty = 0;
 
    QList<QgsMbTiles::TileData> metatileTiles;
    metatileTiles.reserve( metaTile.tiles.size() );
 
    for ( auto it = metaTile.tiles.constBegin(); it != metaTile.tiles.constEnd(); ++it )
    {
      if ( feedback->isCanceled() )
        break;
 
      const QPair<int, int> tm = it.key();
 
      const QImage tileImage = renderedImg.copy( mTileWidth * tm.first, mTileHeight * tm.second, mTileWidth, mTileHeight );
 
      const bool skipTile = mSkipEmptyTiles && ( testEmptyTilesUsingAlpha0 ? QgsImageOperation::isBlankImage( tileImage ) : QgsImageOperation::isSingleColor( tileImage, mBackgroundColor ) );
      if ( skipTile )
      {
        localEmpty++;
        continue;
      }
 
      QByteArray bytes;
      QBuffer buffer( &bytes );
      buffer.open( QIODevice::WriteOnly );
      tileImage.save( &buffer, mTileFormat.toStdString().c_str(), mJpgQuality );
 
      const Tile tile = it.value();
      const int tileY = tile2tms( tile.y, tile.z );
      metatileTiles.append( { tile.z, tile.x, tileY, bytes } );
      localWritten++;
    }
 
    mWriteQueue->push( metatileTiles );
 
    mTilesWritten += localWritten;
    mEmptyTiles += localEmpty;
 
    mActivePostProcessingTasks--;
    checkPipelineFinished( feedback );
  } );
}
 
void QgsXyzTilesMbtilesAlgorithm::doExport( QgsProcessingFeedback *feedback )
{
  mPostProcessingPool = std::make_unique<QThreadPool>();
  mPostProcessingPool->setMaxThreadCount( std::max( 1, mThreadsNumber ) );
 
  PendingTilesToWriteQueue< QgsMbTiles::TileData > queue;
  mWriteQueue = &queue;
 
  QThread *dbThread = QThread::create( [this, &queue]() {
    QList<QgsMbTiles::TileData> batch;
    constexpr int BATCH_SIZE = 10000;
    batch.reserve( BATCH_SIZE );
    while ( queue.popBatch( batch, BATCH_SIZE ) )
    {
      mMbtilesWriter->setTileData( batch );
      batch.clear();
    }
  } );
  dbThread->start();
 
  QEventLoop loop;
  mEventLoop = &loop;
  mJobOwner.reset( new QObject() );
 
  startJobs( feedback );
 
  if ( !mMetaTiles.isEmpty() || !mRendererJobs.isEmpty() || mActivePostProcessingTasks.load() > 0 )
  {
    loop.exec();
  }
 
  for ( auto it = mRendererJobs.constBegin(); it != mRendererJobs.constEnd(); it++ )
  {
    it.key()->cancel();
    it.key()->deleteLater();
  }
  mRendererJobs.clear();
 
  mPostProcessingPool->waitForDone();
  mPostProcessingPool.reset();
 
  queue.setFinished();
  dbThread->wait();
  delete dbThread;
 
  mWriteQueue = nullptr;
  mEventLoop = nullptr;
}
 
 
//
// QgsXyzTilesGpkgAlgorithm
//
 
QString QgsXyzTilesGpkgAlgorithm::name() const
{
  return u"tilesxyzgpkg"_s;
}
 
QString QgsXyzTilesGpkgAlgorithm::displayName() const
{
  return QObject::tr( "Generate XYZ tiles (GeoPackage)" );
}
 
QStringList QgsXyzTilesGpkgAlgorithm::tags() const
{
  return QObject::tr( "tiles,xyz,geopackage,gpkg,raster" ).split( ',' );
}
 
QString QgsXyzTilesGpkgAlgorithm::shortDescription() const
{
  return QObject::tr( "Renders maps to XYZ raster tiles into a GeoPackage raster tile database." );
}
 
QString QgsXyzTilesGpkgAlgorithm::shortHelpString() const
{
  return QObject::tr(
    "This algorithm generates XYZ raster tiles from the current project and saves them into an OGC GeoPackage file.\n\n"
    "All visible map layers from the project will be rendered into tiles across the specified extent and zoom range."
  );
}
 
QgsXyzTilesGpkgAlgorithm *QgsXyzTilesGpkgAlgorithm::createInstance() const
{
  return new QgsXyzTilesGpkgAlgorithm();
}
 
void QgsXyzTilesGpkgAlgorithm::initAlgorithm( const QVariantMap & )
{
  createCommonParameters();
  createTileMatrixParameters();
 
  auto tileWidthParam = std::make_unique<QgsProcessingParameterNumber>( u"TILE_WIDTH"_s, QObject::tr( "Tile width" ), Qgis::ProcessingNumberParameterType::Integer, 256, false, 1, 4096 );
  tileWidthParam->setHelp( QObject::tr( "Width of each tile image in pixels." ) );
  addParameter( tileWidthParam.release() );
 
  auto tileHeightParam = std::make_unique<QgsProcessingParameterNumber>( u"TILE_HEIGHT"_s, QObject::tr( "Tile height" ), Qgis::ProcessingNumberParameterType::Integer, 256, false, 1, 4096 );
  tileHeightParam->setHelp( QObject::tr( "Height of each tile image in pixels." ) );
  addParameter( tileHeightParam.release() );
 
  addParameter( new QgsProcessingParameterFileDestination( u"OUTPUT_FILE"_s, QObject::tr( "Output file" ), QObject::tr( "GeoPackage files (*.gpkg *.GPKG)" ) ) );
 
  addOutput( new QgsProcessingOutputRasterLayer( u"OUTPUT_LAYER"_s, QObject::tr( "Output tiles as raster layer" ) ) );
}
 
QVariantMap QgsXyzTilesGpkgAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  QGS_MARK_ALGORITHM_SOURCE
 
  const QString outputFile = parameterAsString( parameters, u"OUTPUT_FILE"_s, context );
 
  if ( QFile::exists( outputFile ) )
  {
    feedback->pushWarning( QObject::tr( "Removing existing file '%1'" ).arg( QDir::toNativeSeparators( outputFile ) ) );
    if ( !QFile( outputFile ).remove() )
    {
      throw QgsProcessingException( QObject::tr( "Could not remove existing file '%1'" ).arg( QDir::toNativeSeparators( outputFile ) ) );
    }
  }
 
  mGpkgWriter = std::make_unique<QgsGeoPackageTiles>( outputFile );
 
  if ( !mGpkgWriter->create( mZ0matrix, mTileGenerationRegion, mMinZoom, mMaxZoomLimitIncludingOverrides, mTileWidth, mTileHeight ) )
  {
    throw QgsProcessingException( QObject::tr( "Failed to create GeoPackage file %1: %2" ).arg( outputFile, mGpkgWriter->lastError() ) );
  }
 
  long long totalTiles = 0;
  mTotalMetaTiles = 0;
  for ( int z = mMinZoom; z <= mMaxZoomLimitIncludingOverrides; z++ )
  {
    if ( feedback->isCanceled() )
      break;
 
    long long tileCount = 0;
    mMetaTiles += getMetatiles( mZ0matrix, mTileGenerationRegion, z, tileCount, mMetaTileSize, mMaxZoomRegions, mMaxZoom );
    feedback->pushInfo( QObject::tr( "%1 metatiles (%2 tiles) will be created for zoom level %3" ).arg( mMetaTiles.size() - mTotalMetaTiles ).arg( tileCount ).arg( z ) );
    mTotalMetaTiles = mMetaTiles.size();
    totalTiles += tileCount;
  }
  if ( mTotalMetaTiles == 0 )
  {
    throw QgsProcessingException( QObject::tr( "No metatiles will be created -- please check the extent and zoom limits" ) );
  }
  feedback->pushInfo( QObject::tr( "A total of %1 metatiles (%2 tiles) will be created" ).arg( mTotalMetaTiles ).arg( totalTiles ) );
 
  checkLayersUsagePolicy( feedback );
 
  for ( QgsMapLayer *layer : std::as_const( mLayers ) )
  {
    layer->moveToThread( QThread::currentThread() );
  }
  mJobOwner.reset( new QObject() );
 
  doExport( feedback );
 
  qDeleteAll( mLayers );
  mLayers.clear();
 
  if ( !feedback->isCanceled() )
  {
    mGpkgWriter->finalize();
  }
 
  mGpkgWriter->close();
 
  if ( mSkipEmptyTiles )
  {
    feedback->pushInfo( QObject::tr( "Wrote %1 total tiles, skipped %2 empty tiles" ).arg( mTilesWritten.load() ).arg( mEmptyTiles.load() ) );
  }
 
  QVariantMap results;
 
  // try to load the result as a raster layer
  if ( !feedback->isCanceled() )
  {
    auto layer = std::make_unique<QgsRasterLayer>( outputFile, "OUTPUT_LAYER", u"gdal"_s );
    if ( !layer->isValid() )
    {
      feedback->reportError( QObject::tr( "Failed to open GeoPackage file as a raster layer" ) );
    }
    const QString layerId = layer->id();
    const QgsProcessingContext::LayerDetails details( layer->name(), context.project(), u"OUTPUT_LAYER"_s, QgsProcessingUtils::LayerHint::Raster );
    details.setOutputLayerName( layer.get() );
    context.addLayerToLoadOnCompletion( layerId, details );
    context.temporaryLayerStore()->addMapLayer( layer.release() );
    results.insert( u"OUTPUT_LAYER"_s, layerId );
  }
 
  results.insert( u"OUTPUT_FILE"_s, outputFile );
  return results;
}
 
void QgsXyzTilesGpkgAlgorithm::processMetaTile( const MetaTile &metaTile, const QImage &renderedImg, QgsProcessingFeedback *feedback )
{
  mActivePostProcessingTasks++;
  mPostProcessingPool->start( [this, feedback, metaTile, renderedImg]() {
    const bool testEmptyTilesUsingAlpha0 = mTileFormat != "JPG"_L1 && mBackgroundColor.alpha() == 0;
    long long localWritten = 0;
    long long localEmpty = 0;
 
    QList<QgsGeoPackageTiles::TileData> metatileTiles;
    metatileTiles.reserve( metaTile.tiles.size() );
 
    for ( auto it = metaTile.tiles.constBegin(); it != metaTile.tiles.constEnd(); ++it )
    {
      if ( feedback->isCanceled() )
        break;
 
      const QPair<int, int> tm = it.key();
 
      const QImage tileImage = renderedImg.copy( mTileWidth * tm.first, mTileHeight * tm.second, mTileWidth, mTileHeight );
 
      const bool skipTile = mSkipEmptyTiles && ( testEmptyTilesUsingAlpha0 ? QgsImageOperation::isBlankImage( tileImage ) : QgsImageOperation::isSingleColor( tileImage, mBackgroundColor ) );
      if ( skipTile )
      {
        localEmpty++;
        continue;
      }
 
      QByteArray bytes;
      QBuffer buffer( &bytes );
      buffer.open( QIODevice::WriteOnly );
      tileImage.save( &buffer, mTileFormat.toStdString().c_str(), mJpgQuality );
 
      const Tile tile = it.value();
      // GeoPackage uses tile.y directly (Top-Left origin)
      metatileTiles.append( { tile.z, tile.x, tile.y, bytes } );
      localWritten++;
    }
 
    mWriteQueue->push( metatileTiles );
 
    mTilesWritten += localWritten;
    mEmptyTiles += localEmpty;
 
    mActivePostProcessingTasks--;
    checkPipelineFinished( feedback );
  } );
}
 
void QgsXyzTilesGpkgAlgorithm::doExport( QgsProcessingFeedback *feedback )
{
  mPostProcessingPool = std::make_unique<QThreadPool>();
  mPostProcessingPool->setMaxThreadCount( std::max( 1, mThreadsNumber ) );
 
  PendingTilesToWriteQueue<QgsGeoPackageTiles::TileData> queue;
  mWriteQueue = &queue;
 
  QThread *dbThread = QThread::create( [this, &queue]() {
    QList<QgsGeoPackageTiles::TileData> batch;
    constexpr int BATCH_SIZE = 10000;
    batch.reserve( BATCH_SIZE );
    while ( queue.popBatch( batch, BATCH_SIZE ) )
    {
      mGpkgWriter->setTileData( batch );
      batch.clear();
    }
  } );
  dbThread->start();
 
  QEventLoop loop;
  mEventLoop = &loop;
  mJobOwner.reset( new QObject() );
 
  startJobs( feedback );
 
  if ( !mMetaTiles.isEmpty() || !mRendererJobs.isEmpty() || mActivePostProcessingTasks.load() > 0 )
  {
    loop.exec();
  }
 
  for ( auto *j : mRendererJobs.keys() )
  {
    j->cancel();
    j->deleteLater();
  }
  mRendererJobs.clear();
 
  mPostProcessingPool->waitForDone();
  mPostProcessingPool.reset();
 
  queue.setFinished();
  dbThread->wait();
  delete dbThread;
 
  mWriteQueue = nullptr;
  mEventLoop = nullptr;
}