QGIS » QGIS Application

/***************************************************************************

                          qgsrastercalculator.cpp  -  description

                          -----------------------

    begin                : September 28th, 2010

    copyright            : (C) 2010 by Marco Hugentobler

    email                : marco dot hugentobler at sourcepole dot ch

 ***************************************************************************/

/***************************************************************************

 *                                                                         *

 *   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 "qgsgdalutils.h"

#include "qgsrastercalculator.h"

#include "qgsrasterdataprovider.h"

#include "qgsrasterinterface.h"

#include "qgsrasterlayer.h"

#include "qgsrastermatrix.h"

#include "qgsrasterprojector.h"

#include "qgsfeedback.h"

#include "qgsogrutils.h"

#include "qgsproject.h"

#include <QFile>

#include <cpl_string.h>

#include <gdalwarper.h>

#ifdef HAVE_OPENCL

#include "qgsopenclutils.h"

#include "qgsgdalutils.h"

#endif

//

// global callback function

//

int CPL_STDCALL GdalProgressCallback( double dfComplete, const char *pszMessage, void *pProgressArg )

{

  Q_UNUSED( pszMessage )

  static double sDfLastComplete = -1.0;

  QgsFeedback *feedback = static_cast<QgsFeedback *>( pProgressArg );

  if ( sDfLastComplete > dfComplete )

  {

    if ( sDfLastComplete >= 1.0 )

      sDfLastComplete = -1.0;

    else

      sDfLastComplete = dfComplete;

  }

  if ( std::floor( sDfLastComplete * 10 ) != std::floor( dfComplete * 10 ) )

  {

    if ( feedback )

      feedback->setProgress( dfComplete * 100 );

  }

  sDfLastComplete = dfComplete;

  if ( feedback && feedback->isCanceled() )

    return false;

  return true;

}

QgsRasterCalculator::QgsRasterCalculator( const QString &formulaString, const QString &outputFile, const QString &outputFormat, const QgsRectangle &outputExtent, int nOutputColumns, int nOutputRows, const QVector<QgsRasterCalculatorEntry> &rasterEntries, const QgsCoordinateTransformContext &transformContext )

  : mFormulaString( formulaString )

  , mOutputFile( outputFile )

  , mOutputFormat( outputFormat )

  , mOutputRectangle( outputExtent )

  , mNumOutputColumns( nOutputColumns )

  , mNumOutputRows( nOutputRows )

  , mRasterEntries( rasterEntries )

  , mTransformContext( transformContext )

{

}

QgsRasterCalculator::QgsRasterCalculator( const QString &formulaString, const QString &outputFile, const QString &outputFormat, const QgsRectangle &outputExtent, const QgsCoordinateReferenceSystem &outputCrs, int nOutputColumns, int nOutputRows, const QVector<QgsRasterCalculatorEntry> &rasterEntries, const QgsCoordinateTransformContext &transformContext )

  : mFormulaString( formulaString )

  , mOutputFile( outputFile )

  , mOutputFormat( outputFormat )

  , mOutputRectangle( outputExtent )

  , mOutputCrs( outputCrs )

  , mNumOutputColumns( nOutputColumns )

  , mNumOutputRows( nOutputRows )

  , mRasterEntries( rasterEntries )

  , mTransformContext( transformContext )

{

}

// Deprecated!

QgsRasterCalculator::QgsRasterCalculator( const QString &formulaString, const QString &outputFile, const QString &outputFormat, const QgsRectangle &outputExtent, int nOutputColumns, int nOutputRows, const QVector<QgsRasterCalculatorEntry> &rasterEntries )

  : mFormulaString( formulaString )

  , mOutputFile( outputFile )

  , mOutputFormat( outputFormat )

  , mOutputRectangle( outputExtent )

  , mNumOutputColumns( nOutputColumns )

  , mNumOutputRows( nOutputRows )

  , mRasterEntries( rasterEntries )

{

  //default to first layer's crs

  mOutputCrs = mRasterEntries.at( 0 ).raster->crs();

  mTransformContext = QgsProject::instance()->transformContext();

}

// Deprecated!

QgsRasterCalculator::QgsRasterCalculator( const QString &formulaString, const QString &outputFile, const QString &outputFormat, const QgsRectangle &outputExtent, const QgsCoordinateReferenceSystem &outputCrs, int nOutputColumns, int nOutputRows, const QVector<QgsRasterCalculatorEntry> &rasterEntries )

  : mFormulaString( formulaString )

  , mOutputFile( outputFile )

  , mOutputFormat( outputFormat )

  , mOutputRectangle( outputExtent )

  , mOutputCrs( outputCrs )

  , mNumOutputColumns( nOutputColumns )

  , mNumOutputRows( nOutputRows )

  , mRasterEntries( rasterEntries )

  , mTransformContext( QgsProject::instance()->transformContext() )

{

}

QgsRasterCalculator::Result QgsRasterCalculator::processCalculation( QgsFeedback *feedback )

{

  mLastError.clear();

  //prepare search string / tree

  std::unique_ptr<QgsRasterCalcNode> calcNode( QgsRasterCalcNode::parseRasterCalcString( mFormulaString, mLastError ) );

  if ( !calcNode )

  {

    //error

    return ParserError;

  }

  // Check input layers and bands

  for ( const auto &entry : std::as_const( mRasterEntries ) )

  {

    if ( !entry.raster ) // no raster layer in entry

    {

      mLastError = QObject::tr( "No raster layer for entry %1" ).arg( entry.ref );

      return InputLayerError;

    }

    if ( entry.bandNumber <= 0 || entry.bandNumber > entry.raster->bandCount() )

    {

      mLastError = QObject::tr( "Band number %1 is not valid for entry %2" ).arg( entry.bandNumber ).arg( entry.ref );

      return BandError;

    }

  }

  // Check if we need to read the raster as a whole (which is memory inefficient

  // and not interruptible by the user) by checking if any raster matrix nodes are

  // in the expression

  bool requiresMatrix = !calcNode->findNodes( QgsRasterCalcNode::Type::tMatrix ).isEmpty();

#ifdef HAVE_OPENCL

  // Check for matrix nodes, GPU implementation does not support them

  if ( QgsOpenClUtils::enabled() && QgsOpenClUtils::available() && !requiresMatrix )

  {

    return processCalculationGPU( std::move( calcNode ), feedback );

  }

#endif

  //open output dataset for writing

  GDALDriverH outputDriver = openOutputDriver();

  if ( !outputDriver )

  {

    mLastError = QObject::tr( "Could not obtain driver for %1" ).arg( mOutputFormat );

    return CreateOutputError;

  }

  gdal::dataset_unique_ptr outputDataset( openOutputFile( outputDriver ) );

  if ( !outputDataset )

  {

    mLastError = QObject::tr( "Could not create output %1" ).arg( mOutputFile );

    return CreateOutputError;

  }

  GDALSetProjection( outputDataset.get(), mOutputCrs.toWkt( Qgis::CrsWktVariant::PreferredGdal ).toLocal8Bit().data() );

  GDALRasterBandH outputRasterBand = GDALGetRasterBand( outputDataset.get(), 1 );

  float outputNodataValue = -FLT_MAX;

  GDALSetRasterNoDataValue( outputRasterBand, outputNodataValue );

  // Take the fast route (process one line at a time) if we can

  if ( !requiresMatrix )

  {

    // Map of raster names -> blocks

    std::map<QString, std::unique_ptr<QgsRasterBlock>> inputBlocks;

    std::map<QString, QgsRasterCalculatorEntry> uniqueRasterEntries;

    const QList<const QgsRasterCalcNode *> rasterRefNodes = calcNode->findNodes( QgsRasterCalcNode::Type::tRasterRef );

    for ( const QgsRasterCalcNode *r : rasterRefNodes )

    {

      QString layerRef( r->toString().remove( 0, 1 ) );

      layerRef.chop( 1 );

      if ( !inputBlocks.count( layerRef ) )

      {

        for ( const QgsRasterCalculatorEntry &ref : std::as_const( mRasterEntries ) )

        {

          if ( ref.ref == layerRef )

          {

            uniqueRasterEntries[layerRef] = ref;

            inputBlocks[layerRef] = std::make_unique<QgsRasterBlock>();

          }

        }

      }

    }

    //read / write line by line

    QMap<QString, QgsRasterBlock *> _rasterData;

    // Cast to float

    std::vector<float> castedResult( static_cast<size_t>( mNumOutputColumns ), 0 );

    auto rowHeight = mOutputRectangle.height() / mNumOutputRows;

    for ( size_t row = 0; row < static_cast<size_t>( mNumOutputRows ); ++row )

    {

      if ( feedback )

      {

        feedback->setProgress( 100.0 * static_cast<double>( row ) / mNumOutputRows );

      }

      if ( feedback && feedback->isCanceled() )

      {

        break;

      }

      // Calculates the rect for a single row read

      QgsRectangle rect( mOutputRectangle );

      rect.setYMaximum( rect.yMaximum() - rowHeight * row );

      rect.setYMinimum( rect.yMaximum() - rowHeight );

      // Read rows into input blocks

      for ( auto &layerRef : inputBlocks )

      {

        QgsRasterCalculatorEntry ref = uniqueRasterEntries[layerRef.first];

        if ( ref.raster->crs() != mOutputCrs )

        {

          QgsRasterProjector proj;

          proj.setCrs( ref.raster->crs(), mOutputCrs, mTransformContext );

          proj.setInput( ref.raster->dataProvider() );

          proj.setPrecision( QgsRasterProjector::Exact );

          layerRef.second.reset( proj.block( ref.bandNumber, rect, mNumOutputColumns, 1 ) );

        }

        else

        {

          layerRef.second.reset( ref.raster->dataProvider()->block( ref.bandNumber, rect, mNumOutputColumns, 1 ) );

        }

      }

      // 1 row X mNumOutputColumns matrix

      QgsRasterMatrix resultMatrix( mNumOutputColumns, 1, nullptr, outputNodataValue );

      _rasterData.clear();

      for ( const auto &layerRef : inputBlocks )

      {

        _rasterData.insert( layerRef.first, layerRef.second.get() );

      }

      if ( calcNode->calculate( _rasterData, resultMatrix, 0 ) )

      {

        std::copy( resultMatrix.data(), resultMatrix.data() + mNumOutputColumns, castedResult.begin() );

        if ( GDALRasterIO( outputRasterBand, GF_Write, 0, row, mNumOutputColumns, 1, castedResult.data(), mNumOutputColumns, 1, GDT_Float32, 0, 0 ) != CE_None )

        {

          QgsDebugError( QStringLiteral( "RasterIO error!" ) );

        }

      }

      else

      {

        //delete the dataset without closing (because it is faster)

        gdal::fast_delete_and_close( outputDataset, outputDriver, mOutputFile );

        return CalculationError;

      }

    }

    if ( feedback )

    {

      feedback->setProgress( 100.0 );

    }

  }

  else // Original code (memory inefficient route)

  {

    QMap<QString, QgsRasterBlock *> inputBlocks;

    QVector<QgsRasterCalculatorEntry>::const_iterator it = mRasterEntries.constBegin();

    for ( ; it != mRasterEntries.constEnd(); ++it )

    {

      std::unique_ptr<QgsRasterBlock> block;

      // if crs transform needed

      if ( it->raster->crs() != mOutputCrs )

      {

        QgsRasterProjector proj;

        proj.setCrs( it->raster->crs(), mOutputCrs, it->raster->transformContext() );

        proj.setInput( it->raster->dataProvider() );

        proj.setPrecision( QgsRasterProjector::Exact );

        QgsRasterBlockFeedback *rasterBlockFeedback = new QgsRasterBlockFeedback();

        QObject::connect( feedback, &QgsFeedback::canceled, rasterBlockFeedback, &QgsRasterBlockFeedback::cancel );

        block.reset( proj.block( it->bandNumber, mOutputRectangle, mNumOutputColumns, mNumOutputRows, rasterBlockFeedback ) );

        if ( rasterBlockFeedback->isCanceled() )

        {

          qDeleteAll( inputBlocks );

          return Canceled;

        }

      }

      else

      {

        block.reset( it->raster->dataProvider()->block( it->bandNumber, mOutputRectangle, mNumOutputColumns, mNumOutputRows ) );

      }

      if ( block->isEmpty() )

      {

        mLastError = QObject::tr( "Could not allocate required memory for %1" ).arg( it->ref );

        qDeleteAll( inputBlocks );

        return MemoryError;

      }

      inputBlocks.insert( it->ref, block.release() );

    }

    QgsRasterMatrix resultMatrix;

    resultMatrix.setNodataValue( outputNodataValue );

    //read / write line by line

    for ( int i = 0; i < mNumOutputRows; ++i )

    {

      if ( feedback )

      {

        feedback->setProgress( 100.0 * static_cast<double>( i ) / mNumOutputRows );

      }

      if ( feedback && feedback->isCanceled() )

      {

        break;

      }

      if ( calcNode->calculate( inputBlocks, resultMatrix, i ) )

      {

        bool resultIsNumber = resultMatrix.isNumber();

        float *calcData = new float[mNumOutputColumns];

        for ( int j = 0; j < mNumOutputColumns; ++j )

        {

          calcData[j] = ( float ) ( resultIsNumber ? resultMatrix.number() : resultMatrix.data()[j] );

        }

        //write scanline to the dataset

        if ( GDALRasterIO( outputRasterBand, GF_Write, 0, i, mNumOutputColumns, 1, calcData, mNumOutputColumns, 1, GDT_Float32, 0, 0 ) != CE_None )

        {

          QgsDebugError( QStringLiteral( "RasterIO error!" ) );

        }

        delete[] calcData;

      }

      else

      {

        qDeleteAll( inputBlocks );

        inputBlocks.clear();

        gdal::fast_delete_and_close( outputDataset, outputDriver, mOutputFile );

        return CalculationError;

      }

    }

    if ( feedback )

    {

      feedback->setProgress( 100.0 );

    }

    //close datasets and release memory

    calcNode.reset();

    qDeleteAll( inputBlocks );

    inputBlocks.clear();

  }

  if ( feedback && feedback->isCanceled() )

  {

    //delete the dataset without closing (because it is faster)

    gdal::fast_delete_and_close( outputDataset, outputDriver, mOutputFile );

    return Canceled;

  }

  GDALComputeRasterStatistics( outputRasterBand, true, nullptr, nullptr, nullptr, nullptr, GdalProgressCallback, feedback );

  return Success;

}

#ifdef HAVE_OPENCL

QgsRasterCalculator::Result QgsRasterCalculator::processCalculationGPU( std::unique_ptr<QgsRasterCalcNode> calcNode, QgsFeedback *feedback )

{

  QString cExpression( calcNode->toString( true ) );

  QList<const QgsRasterCalcNode *> nodeList( calcNode->findNodes( QgsRasterCalcNode::Type::tRasterRef ) );

  QSet<QString> capturedTexts;

  for ( const auto &r : std::as_const( nodeList ) )

  {

    QString s( r->toString().remove( 0, 1 ) );

    s.chop( 1 );

    capturedTexts.insert( s );

  }

  // Extract all references

  struct LayerRef

  {

      QString name;

      int band;

      QgsRasterLayer *layer = nullptr;

      QString varName;

      QString typeName;

      size_t index;

      size_t bufferSize;

      size_t dataSize;

  };

  // Collects all layers, band, name, varName and size information

  std::vector<LayerRef> inputRefs;

  size_t refCounter = 0;

  for ( const auto &r : capturedTexts )

  {

    if ( r.startsWith( '"' ) )

      continue;

    QStringList parts( r.split( '@' ) );

    if ( parts.count() != 2 )

      continue;

    bool ok = false;

    LayerRef entry;

    entry.name = r;

    entry.band = parts[1].toInt( &ok );

    for ( const auto &ref : std::as_const( mRasterEntries ) )

    {

      if ( ref.ref == entry.name )

        entry.layer = ref.raster;

    }

    if ( !( entry.layer && entry.layer->dataProvider() && ok ) )

      continue;

    entry.dataSize = entry.layer->dataProvider()->dataTypeSize( entry.band );

    switch ( entry.layer->dataProvider()->dataType( entry.band ) )

    {

      case Qgis::DataType::Byte:

        entry.typeName = QStringLiteral( "unsigned char" );

        break;

      case Qgis::DataType::Int8:

        entry.typeName = QStringLiteral( "signed char" );

        break;

      case Qgis::DataType::UInt16:

        entry.typeName = QStringLiteral( "unsigned int" );

        break;

      case Qgis::DataType::Int16:

        entry.typeName = QStringLiteral( "short" );

        break;

      case Qgis::DataType::UInt32:

        entry.typeName = QStringLiteral( "unsigned int" );

        break;

      case Qgis::DataType::Int32:

        entry.typeName = QStringLiteral( "int" );

        break;

      case Qgis::DataType::Float32:

        entry.typeName = QStringLiteral( "float" );

        break;

      // FIXME: not sure all OpenCL implementations support double

      //        maybe safer to fall back to the CPU implementation

      //        after a compatibility check

      case Qgis::DataType::Float64:

        entry.typeName = QStringLiteral( "double" );

        break;

      case Qgis::DataType::CInt16:

      case Qgis::DataType::CInt32:

      case Qgis::DataType::CFloat32:

      case Qgis::DataType::CFloat64:

      case Qgis::DataType::ARGB32:

      case Qgis::DataType::ARGB32_Premultiplied:

      case Qgis::DataType::UnknownDataType:

        return BandError;

    }

    entry.bufferSize = entry.dataSize * mNumOutputColumns;

    entry.index = refCounter;

    entry.varName = QStringLiteral( "input_raster_%1_band_%2" )

                      .arg( refCounter++ )

                      .arg( entry.band );

    inputRefs.push_back( entry );

  }

  // May throw an openCL exception

  try

  {

    // Prepare context and queue

    cl::Context ctx( QgsOpenClUtils::context() );

    cl::CommandQueue queue( QgsOpenClUtils::commandQueue() );

    // Create the C expression

    std::vector<cl::Buffer> inputBuffers;

    inputBuffers.reserve( inputRefs.size() );

    QStringList inputArgs;

    for ( const auto &ref : inputRefs )

    {

      cExpression.replace( QStringLiteral( "\"%1\"" ).arg( ref.name ), QStringLiteral( "%1[i]" ).arg( ref.varName ) );

      inputArgs.append( QStringLiteral( "__global %1 *%2" )

                          .arg( ref.typeName, ref.varName ) );

      inputBuffers.push_back( cl::Buffer( ctx, CL_MEM_READ_ONLY, ref.bufferSize, nullptr, nullptr ) );

    }

    //qDebug() << cExpression;

    // Create the program

    QString programTemplate( R"CL(

    // Inputs:

    ##INPUT_DESC##

    // Expression: ##EXPRESSION_ORIGINAL##

    __kernel void rasterCalculator( ##INPUT##

                              __global float *resultLine

                            )

    {

      // Get the index of the current element

      const int i = get_global_id(0);

      // Check for nodata in input

      if ( ##INPUT_NODATA_CHECK## )

        resultLine[i] = -FLT_MAX;

      // Expression

      else

        resultLine[i] = ##EXPRESSION##;

    }

    )CL" );

    QStringList inputDesc;

    QStringList inputNoDataCheck;

    for ( const auto &ref : inputRefs )

    {

      inputDesc.append( QStringLiteral( "  // %1 = %2" ).arg( ref.varName, ref.name ) );

      if ( ref.layer->dataProvider()->sourceHasNoDataValue( ref.band ) )

      {

        inputNoDataCheck.append( QStringLiteral( "(float) %1[i] == (float) %2" ).arg( ref.varName, QString::number( ref.layer->dataProvider()->sourceNoDataValue( ref.band ), 'g', 10 ) ) );

      }

    }

    programTemplate = programTemplate.replace( QLatin1String( "##INPUT_NODATA_CHECK##" ), inputNoDataCheck.isEmpty() ? QStringLiteral( "false" ) : inputNoDataCheck.join( QLatin1String( " || " ) ) );

    programTemplate = programTemplate.replace( QLatin1String( "##INPUT_DESC##" ), inputDesc.join( '\n' ) );

    programTemplate = programTemplate.replace( QLatin1String( "##INPUT##" ), !inputArgs.isEmpty() ? ( inputArgs.join( ',' ).append( ',' ) ) : QChar( ' ' ) );

    programTemplate = programTemplate.replace( QLatin1String( "##EXPRESSION##" ), cExpression );

    programTemplate = programTemplate.replace( QLatin1String( "##EXPRESSION_ORIGINAL##" ), calcNode->toString() );

    //qDebug() << programTemplate;

    // Create a program from the kernel source

    cl::Program program( QgsOpenClUtils::buildProgram( programTemplate, QgsOpenClUtils::ExceptionBehavior::Throw ) );

    // Create the buffers, output is float32 (4 bytes)

    // We assume size of float = 4 because that's the size used by OpenCL and IEEE 754

    Q_ASSERT( sizeof( float ) == 4 );

    std::size_t resultBufferSize( 4 * static_cast<size_t>( mNumOutputColumns ) );

    cl::Buffer resultLineBuffer( ctx, CL_MEM_WRITE_ONLY, resultBufferSize, nullptr, nullptr );

    auto kernel = cl::Kernel( program, "rasterCalculator" );

    for ( unsigned int i = 0; i < inputBuffers.size(); i++ )

    {

      kernel.setArg( i, inputBuffers.at( i ) );

    }

    kernel.setArg( static_cast<unsigned int>( inputBuffers.size() ), resultLineBuffer );

    QgsOpenClUtils::CPLAllocator<float> resultLine( static_cast<size_t>( mNumOutputColumns ) );

    //open output dataset for writing

    GDALDriverH outputDriver = openOutputDriver();

    if ( !outputDriver )

    {

      mLastError = QObject::tr( "Could not obtain driver for %1" ).arg( mOutputFormat );

      return CreateOutputError;

    }

    gdal::dataset_unique_ptr outputDataset( openOutputFile( outputDriver ) );

    if ( !outputDataset )

    {

      mLastError = QObject::tr( "Could not create output %1" ).arg( mOutputFile );

      return CreateOutputError;

    }

    GDALSetProjection( outputDataset.get(), mOutputCrs.toWkt( Qgis::CrsWktVariant::PreferredGdal ).toLocal8Bit().data() );

    GDALRasterBandH outputRasterBand = GDALGetRasterBand( outputDataset.get(), 1 );

    if ( !outputRasterBand )

      return BandError;

    const float outputNodataValue = -FLT_MAX;

    GDALSetRasterNoDataValue( outputRasterBand, outputNodataValue );

    // Input block (buffer)

    std::unique_ptr<QgsRasterBlock> block;

    // Run kernel on all scanlines

    auto rowHeight = mOutputRectangle.height() / mNumOutputRows;

    for ( int line = 0; line < mNumOutputRows; line++ )

    {

      if ( feedback && feedback->isCanceled() )

      {

        break;

      }

      if ( feedback )

      {

        feedback->setProgress( 100.0 * static_cast<double>( line ) / mNumOutputRows );

      }

      // Read lines from rasters into the buffers

      for ( const auto &ref : inputRefs )

      {

        // Read one row

        QgsRectangle rect( mOutputRectangle );

        rect.setYMaximum( rect.yMaximum() - rowHeight * line );

        rect.setYMinimum( rect.yMaximum() - rowHeight );

        // TODO: check if this is too slow

        // if crs transform needed

        if ( ref.layer->crs() != mOutputCrs )

        {

          QgsRasterProjector proj;

          proj.setCrs( ref.layer->crs(), mOutputCrs, ref.layer->transformContext() );

          proj.setInput( ref.layer->dataProvider() );

          proj.setPrecision( QgsRasterProjector::Exact );

          block.reset( proj.block( ref.band, rect, mNumOutputColumns, 1 ) );

        }

        else

        {

          block.reset( ref.layer->dataProvider()->block( ref.band, rect, mNumOutputColumns, 1 ) );

        }

        //for ( int i = 0; i < mNumOutputColumns; i++ )

        //  qDebug() << "Input: " << line << i << ref.varName << " = " << block->value( 0, i );

        //qDebug() << "Writing buffer " << ref.index;

        Q_ASSERT( ref.bufferSize == static_cast<size_t>( block->data().size() ) );

        queue.enqueueWriteBuffer( inputBuffers[ref.index], CL_TRUE, 0, ref.bufferSize, block->bits() );

      }

      // Run the kernel

      queue.enqueueNDRangeKernel(

        kernel,

        0,

        cl::NDRange( mNumOutputColumns )

      );

      // Write the result

      queue.enqueueReadBuffer( resultLineBuffer, CL_TRUE, 0, resultBufferSize, resultLine.get() );

      //for ( int i = 0; i < mNumOutputColumns; i++ )

      //  qDebug() << "Output: " << line << i << " = " << resultLine[i];

      if ( GDALRasterIO( outputRasterBand, GF_Write, 0, line, mNumOutputColumns, 1, resultLine.get(), mNumOutputColumns, 1, GDT_Float32, 0, 0 ) != CE_None )

      {

        return CreateOutputError;

      }

    }

    if ( feedback && feedback->isCanceled() )

    {

      //delete the dataset without closing (because it is faster)

      gdal::fast_delete_and_close( outputDataset, outputDriver, mOutputFile );

      return Canceled;

    }

    inputBuffers.clear();

    GDALComputeRasterStatistics( outputRasterBand, true, nullptr, nullptr, nullptr, nullptr, GdalProgressCallback, feedback );

  }

  catch ( cl::Error &e )

  {

    mLastError = e.what();

    return CreateOutputError;

  }

  return Success;

}

#endif

GDALDriverH QgsRasterCalculator::openOutputDriver()

{

  //open driver

  GDALDriverH outputDriver = GDALGetDriverByName( mOutputFormat.toLocal8Bit().data() );

  if ( !outputDriver )

  {

    return outputDriver; //return nullptr, driver does not exist

  }

  if ( !QgsGdalUtils::supportsRasterCreate( outputDriver ) )

  {

    return nullptr; //driver exist, but it does not support the create operation

  }

  return outputDriver;

}

gdal::dataset_unique_ptr QgsRasterCalculator::openOutputFile( GDALDriverH outputDriver )

{

  //open output file

  char **papszOptions = nullptr;

  gdal::dataset_unique_ptr outputDataset( GDALCreate( outputDriver, mOutputFile.toUtf8().constData(), mNumOutputColumns, mNumOutputRows, 1, GDT_Float32, papszOptions ) );

  if ( !outputDataset )

  {

    return nullptr;

  }

  //assign georef information

  double geotransform[6];

  outputGeoTransform( geotransform );

  GDALSetGeoTransform( outputDataset.get(), geotransform );

  return outputDataset;

}

void QgsRasterCalculator::outputGeoTransform( double *transform ) const

{

  transform[0] = mOutputRectangle.xMinimum();

  transform[1] = mOutputRectangle.width() / mNumOutputColumns;

  transform[2] = 0;

  transform[3] = mOutputRectangle.yMaximum();

  transform[4] = 0;

  transform[5] = -mOutputRectangle.height() / mNumOutputRows;

}

QString QgsRasterCalculator::lastError() const

{

  return mLastError;

}

QVector<QgsRasterCalculatorEntry> QgsRasterCalculatorEntry::rasterEntries()

{

  QVector<QgsRasterCalculatorEntry> availableEntries;

  const QMap<QString, QgsMapLayer *> &layers = QgsProject::instance()->mapLayers();

  auto uniqueRasterBandIdentifier = [&]( QgsRasterCalculatorEntry &entry ) -> bool {

    unsigned int i( 1 );

    entry.ref = QStringLiteral( "%1@%2" ).arg( entry.raster->name() ).arg( entry.bandNumber );

    while ( true )

    {

      bool unique( true );

      for ( const auto &ref : std::as_const( availableEntries ) )

      {

        // Safety belt

        if ( !( entry.raster && ref.raster ) )

          continue;

        // Check if is another band of the same raster

        if ( ref.raster->publicSource() == entry.raster->publicSource() )

        {

          if ( ref.bandNumber != entry.bandNumber )

          {

            continue;

          }

          else // a layer with the same data source was already added to the list

          {

            return false;

          }

        }

        // If same name but different source

        if ( ref.ref == entry.ref )

        {

          unique = false;

          entry.ref = QStringLiteral( "%1_%2@%3" ).arg( entry.raster->name() ).arg( i++ ).arg( entry.bandNumber );

        }

      }

      if ( unique )

        return true;

    }

  };

  QMap<QString, QgsMapLayer *>::const_iterator layerIt = layers.constBegin();

  for ( ; layerIt != layers.constEnd(); ++layerIt )

  {

    QgsRasterLayer *rlayer = qobject_cast<QgsRasterLayer *>( layerIt.value() );

    if ( rlayer && rlayer->dataProvider() && ( rlayer->dataProvider()->capabilities() & Qgis::RasterInterfaceCapability::Size ) )

    {

      //get number of bands

      for ( int i = 0; i < rlayer->bandCount(); ++i )

      {

        QgsRasterCalculatorEntry entry;

        entry.raster = rlayer;

        entry.bandNumber = i + 1;

        if ( !uniqueRasterBandIdentifier( entry ) )

          break;

        availableEntries.push_back( entry );

      }

    }

  }

  return availableEntries;

}