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[FEATURE][processing] New algorithm for extracting binary blobs from fields
Allows users to extract binary fields to files. The filename is set via a data defined expression, so can be taken from a column value or a more complex expression.
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‎src/analysis/CMakeLists.txt

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@@ -41,6 +41,7 @@ SET(QGIS_ANALYSIS_SRCS
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processing/qgsalgorithmexplodehstore.cpp
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processing/qgsalgorithmextendlines.cpp
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processing/qgsalgorithmextenttolayer.cpp
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processing/qgsalgorithmextractbinary.cpp
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processing/qgsalgorithmextractbyattribute.cpp
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processing/qgsalgorithmextractbyexpression.cpp
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processing/qgsalgorithmextractbyextent.cpp

‎src/analysis/processing/qgsalgorithmextractbinary.cpp

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/***************************************************************************
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qgsalgorithmextractbinary.cpp
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-----------------------------------
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begin : November 2018
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copyright : (C) 2018 by Nyall Dawson
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email : nyall dot dawson at gmail dot com
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***************************************************************************/
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/***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************/
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#include "qgsalgorithmextractbinary.h"
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#include "qgsfeaturerequest.h"
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///@cond PRIVATE
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QString QgsExtractBinaryFieldAlgorithm::name() const
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{
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return QStringLiteral( "extractbinary" );
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}
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QString QgsExtractBinaryFieldAlgorithm::displayName() const
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{
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return QObject::tr( "Extract binary field" );
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}
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QString QgsExtractBinaryFieldAlgorithm::shortHelpString() const
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{
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return QObject::tr( "This algorithm extracts contents from a binary field, saving them to individual files." );
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}
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QString QgsExtractBinaryFieldAlgorithm::shortDescription() const
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{
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return QObject::tr( "This algorithm extracts contents from a binary field, saving them to individual files." );
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}
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QStringList QgsExtractBinaryFieldAlgorithm::tags() const
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{
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return QObject::tr( "blob,binaries,save,file,contents,field,column" ).split( ',' );
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}
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QString QgsExtractBinaryFieldAlgorithm::group() const
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{
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return QObject::tr( "Vector table" );
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}
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QString QgsExtractBinaryFieldAlgorithm::groupId() const
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{
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return QStringLiteral( "vectortable" );
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}
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QgsExtractBinaryFieldAlgorithm *QgsExtractBinaryFieldAlgorithm::createInstance() const
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{
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return new QgsExtractBinaryFieldAlgorithm();
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}
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void QgsExtractBinaryFieldAlgorithm::initAlgorithm( const QVariantMap & )
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{
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addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ),
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QObject::tr( "Input layer" ), QList< int>() << QgsProcessing::TypeVector ) );
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addParameter( new QgsProcessingParameterField( QStringLiteral( "FIELD" ), QObject::tr( "Binary field" ), QVariant(),
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QStringLiteral( "INPUT" ), QgsProcessingParameterField::Any ) );
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std::unique_ptr< QgsProcessingParameterString > fileNameParam = qgis::make_unique< QgsProcessingParameterString >( QStringLiteral( "FILENAME" ), QObject::tr( "File name" ) );
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fileNameParam->setIsDynamic( true );
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fileNameParam->setDynamicPropertyDefinition( QgsPropertyDefinition( QStringLiteral( "Filename" ), QObject::tr( "File name" ), QgsPropertyDefinition::String ) );
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fileNameParam->setDynamicLayerParameterName( QStringLiteral( "INPUT" ) );
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addParameter( fileNameParam.release() );
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addParameter( new QgsProcessingParameterFolderDestination( QStringLiteral( "FOLDER" ), QObject::tr( "Destination folder" ) ) );
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}
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QVariantMap QgsExtractBinaryFieldAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
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{
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std::unique_ptr< QgsProcessingFeatureSource > input( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
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if ( !input )
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throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
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QString fieldName = parameterAsString( parameters, QStringLiteral( "FIELD" ), context );
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int fieldIndex = input->fields().lookupField( fieldName );
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if ( fieldIndex < 0 )
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throw QgsProcessingException( QObject::tr( "Invalid binary field" ) );
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const QString folder = parameterAsString( parameters, QStringLiteral( "FOLDER" ), context );
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if ( !QFileInfo::exists( folder ) )
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throw QgsProcessingException( QObject::tr( "Destination folder %1 does not exist" ).arg( folder ) );
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QDir dir( folder );
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const QString filename = parameterAsString( parameters, QStringLiteral( "FILENAME" ), context );
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bool dynamicFilename = QgsProcessingParameters::isDynamic( parameters, QStringLiteral( "FILENAME" ) );
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QgsExpressionContext expressionContext = createExpressionContext( parameters, context, input.get() );
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QgsProperty filenameProperty;
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QSet< QString > fields;
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fields.insert( fieldName );
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QgsFeatureRequest request;
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if ( dynamicFilename )
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{
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filenameProperty = parameters.value( QStringLiteral( "FILENAME" ) ).value< QgsProperty >();
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filenameProperty.prepare( expressionContext );
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fields.unite( filenameProperty.referencedFields() );
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}
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request.setSubsetOfAttributes( fields, input->fields() ).setFlags( QgsFeatureRequest::NoGeometry );
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QgsFeatureIterator features = input->getFeatures( request, QgsProcessingFeatureSource::FlagSkipGeometryValidityChecks );
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double step = input->featureCount() > 0 ? 100.0 / input->featureCount() : 1;
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int i = 0;
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QgsFeature feat;
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while ( features.nextFeature( feat ) )
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{
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i++;
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if ( feedback->isCanceled() )
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{
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break;
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}
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feedback->setProgress( i * step );
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QByteArray ba = feat.attribute( fieldIndex ).toByteArray();
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if ( ba.isEmpty() )
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continue;
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QString name = filename;
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if ( dynamicFilename )
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{
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expressionContext.setFeature( feat );
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name = filenameProperty.valueAsString( expressionContext, name );
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}
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const QString path = dir.filePath( name );
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QFile file( path );
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if ( !file.open( QIODevice::WriteOnly | QFile::Truncate ) )
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{
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feedback->reportError( QObject::tr( "Could not open %1 for writing" ).arg( path ) );
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}
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else
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{
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file.write( ba );
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file.close();
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feedback->pushInfo( QObject::tr( "Extracted %1" ).arg( path ) );
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}
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}
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QVariantMap outputs;
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outputs.insert( QStringLiteral( "FOLDER" ), folder );
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return outputs;
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}
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///@endcond

‎src/analysis/processing/qgsalgorithmextractbinary.h

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/***************************************************************************
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qgsalgorithmextractbinary.h
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---------------------------------
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begin : November 2018
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copyright : (C) 2018 by Nyall Dawson
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email : nyall dot dawson at gmail dot com
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***************************************************************************/
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/***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************/
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#ifndef QGSALGORITHMEXTRACTBINARY_H
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#define QGSALGORITHMEXTRACTBINARY_H
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#define SIP_NO_FILE
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#include "qgis.h"
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#include "qgsprocessingalgorithm.h"
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///@cond PRIVATE
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/**
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* Native extract binary field algorithm.
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*/
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class QgsExtractBinaryFieldAlgorithm : public QgsProcessingAlgorithm
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{
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public:
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QgsExtractBinaryFieldAlgorithm() = default;
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QString name() const override;
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QString displayName() const override;
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QStringList tags() const override;
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QString group() const override;
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QString groupId() const override;
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QString shortHelpString() const override;
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QString shortDescription() const override;
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void initAlgorithm( const QVariantMap &configuration = QVariantMap() ) override;
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QgsExtractBinaryFieldAlgorithm *createInstance() const override SIP_FACTORY;
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protected:
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QVariantMap processAlgorithm( const QVariantMap &parameters,
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QgsProcessingContext &context, QgsProcessingFeedback *feedback ) override;
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};
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///@endcond PRIVATE
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#endif // QGSALGORITHMEXTRACTBINARY_H
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‎src/analysis/processing/qgsnativealgorithms.cpp

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#include "qgsalgorithmexplodehstore.h"
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#include "qgsalgorithmextendlines.h"
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#include "qgsalgorithmextenttolayer.h"
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#include "qgsalgorithmextractbinary.h"
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#include "qgsalgorithmextractbyattribute.h"
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#include "qgsalgorithmextractbyexpression.h"
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#include "qgsalgorithmextractbyextent.h"
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addAlgorithm( new QgsExplodeHstoreAlgorithm() );
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addAlgorithm( new QgsExtendLinesAlgorithm() );
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addAlgorithm( new QgsExtentToLayerAlgorithm() );
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addAlgorithm( new QgsExtractBinaryFieldAlgorithm() );
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addAlgorithm( new QgsExtractByAttributeAlgorithm() );
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addAlgorithm( new QgsExtractByExpressionAlgorithm() );
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addAlgorithm( new QgsExtractByExtentAlgorithm() );

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