QGIS API Documentation 3.39.0-Master (67e056379ed)
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qgsalgorithmextractbinary.cpp
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1/***************************************************************************
2 qgsalgorithmextractbinary.cpp
3 -----------------------------------
4 begin : November 2018
5 copyright : (C) 2018 by Nyall Dawson
6 email : nyall dot dawson at gmail dot com
7 ***************************************************************************/
8
9/***************************************************************************
10 * *
11 * This program is free software; you can redistribute it and/or modify *
12 * it under the terms of the GNU General Public License as published by *
13 * the Free Software Foundation; either version 2 of the License, or *
14 * (at your option) any later version. *
15 * *
16 ***************************************************************************/
17
19#include "qgsfeaturerequest.h"
20
22
23QString QgsExtractBinaryFieldAlgorithm::name() const
24{
25 return QStringLiteral( "extractbinary" );
26}
27
28QString QgsExtractBinaryFieldAlgorithm::displayName() const
29{
30 return QObject::tr( "Extract binary field" );
31}
32
33QString QgsExtractBinaryFieldAlgorithm::shortHelpString() const
34{
35 return QObject::tr( "This algorithm extracts contents from a binary field, saving them to individual files.\n\n"
36 "Filenames can be generated using values taken from "
37 "an attribute in the source table or based on a more complex expression." );
38}
39
40QString QgsExtractBinaryFieldAlgorithm::shortDescription() const
41{
42 return QObject::tr( "This algorithm extracts contents from a binary field, saving them to individual files." );
43}
44
45QStringList QgsExtractBinaryFieldAlgorithm::tags() const
46{
47 return QObject::tr( "blob,binaries,save,file,contents,field,column" ).split( ',' );
48}
49
50QString QgsExtractBinaryFieldAlgorithm::group() const
51{
52 return QObject::tr( "Vector table" );
53}
54
55QString QgsExtractBinaryFieldAlgorithm::groupId() const
56{
57 return QStringLiteral( "vectortable" );
58}
59
60QgsExtractBinaryFieldAlgorithm *QgsExtractBinaryFieldAlgorithm::createInstance() const
61{
62 return new QgsExtractBinaryFieldAlgorithm();
63}
64
65void QgsExtractBinaryFieldAlgorithm::initAlgorithm( const QVariantMap & )
66{
67 addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ),
68 QObject::tr( "Input layer" ), QList< int>() << static_cast< int >( Qgis::ProcessingSourceType::Vector ) ) );
69
70 addParameter( new QgsProcessingParameterField( QStringLiteral( "FIELD" ), QObject::tr( "Binary field" ), QVariant(),
71 QStringLiteral( "INPUT" ), Qgis::ProcessingFieldParameterDataType::Any ) );
72
73 addParameter( new QgsProcessingParameterExpression( QStringLiteral( "FILENAME" ), QObject::tr( "File name" ), QVariant(), QStringLiteral( "INPUT" ) ) );
74
75 addParameter( new QgsProcessingParameterFolderDestination( QStringLiteral( "FOLDER" ), QObject::tr( "Destination folder" ) ) );
76}
77
78QVariantMap QgsExtractBinaryFieldAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
79{
80 std::unique_ptr< QgsProcessingFeatureSource > input( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
81 if ( !input )
82 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
83
84 const QString fieldName = parameterAsString( parameters, QStringLiteral( "FIELD" ), context );
85 const int fieldIndex = input->fields().lookupField( fieldName );
86 if ( fieldIndex < 0 )
87 throw QgsProcessingException( QObject::tr( "Invalid binary field" ) );
88
89 const QString folder = parameterAsString( parameters, QStringLiteral( "FOLDER" ), context );
90 if ( !QFileInfo::exists( folder ) )
91 throw QgsProcessingException( QObject::tr( "Destination folder %1 does not exist" ).arg( folder ) );
92
93 const QDir dir( folder );
94 const QString filenameExpressionString = parameterAsString( parameters, QStringLiteral( "FILENAME" ), context );
95 QgsExpressionContext expressionContext = createExpressionContext( parameters, context, input.get() );
96
97 QSet< QString > fields;
98 fields.insert( fieldName );
99 QgsFeatureRequest request;
100
101 QgsExpression filenameExpression( filenameExpressionString );
102 filenameExpression.prepare( &expressionContext );
103 fields.unite( filenameExpression.referencedColumns() );
104 request.setSubsetOfAttributes( fields, input->fields() );
105 if ( !filenameExpression.needsGeometry() )
107
109 const double step = input->featureCount() > 0 ? 100.0 / input->featureCount() : 1;
110 int i = 0;
111 QgsFeature feat;
112 while ( features.nextFeature( feat ) )
113 {
114 i++;
115 if ( feedback->isCanceled() )
116 {
117 break;
118 }
119
120 feedback->setProgress( i * step );
121
122 const QByteArray ba = feat.attribute( fieldIndex ).toByteArray();
123 if ( ba.isEmpty() )
124 continue;
125
126 expressionContext.setFeature( feat );
127 const QString name = filenameExpression.evaluate( &expressionContext ).toString();
128 if ( filenameExpression.hasEvalError() )
129 {
130 feedback->reportError( QObject::tr( "Error evaluating filename: %1" ).arg( filenameExpression.evalErrorString() ) );
131 continue;
132 }
133
134 const QString path = dir.filePath( name );
135 QFile file( path );
136 if ( !file.open( QIODevice::WriteOnly | QFile::Truncate ) )
137 {
138 feedback->reportError( QObject::tr( "Could not open %1 for writing" ).arg( path ) );
139 }
140 else
141 {
142 file.write( ba );
143 file.close();
144 feedback->pushInfo( QObject::tr( "Extracted %1" ).arg( path ) );
145 }
146 }
147
148 QVariantMap outputs;
149 outputs.insert( QStringLiteral( "FOLDER" ), folder );
150 return outputs;
151}
152
153
@ Vector
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...
@ NoGeometry
Geometry is not required. It may still be returned if e.g. required for a filter condition.
@ SkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
Expression contexts are used to encapsulate the parameters around which a QgsExpression should be eva...
void setFeature(const QgsFeature &feature)
Convenience function for setting a feature for the context.
Class for parsing and evaluation of expressions (formerly called "search strings").
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
Fetch next feature and stores in f, returns true on success.
This class wraps a request for features to a vector layer (or directly its vector data provider).
QgsFeatureRequest & setFlags(Qgis::FeatureRequestFlags flags)
Sets flags that affect how features will be fetched.
QgsFeatureRequest & setSubsetOfAttributes(const QgsAttributeList &attrs)
Set a subset of attributes that will be fetched.
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:58
Q_INVOKABLE QVariant attribute(const QString &name) const
Lookup attribute value by attribute name.
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition qgsfeedback.h:53
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition qgsfeedback.h:61
Contains information about the context in which a processing algorithm is executed.
Custom exception class for processing related exceptions.
Base class for providing feedback from a processing algorithm.
virtual void pushInfo(const QString &info)
Pushes a general informational message from the algorithm.
virtual void reportError(const QString &error, bool fatalError=false)
Reports that the algorithm encountered an error while executing.
An expression parameter for processing algorithms.
An input feature source (such as vector layers) parameter for processing algorithms.
A vector layer or feature source field parameter for processing algorithms.
A folder destination parameter, for specifying the destination path for a folder created by the algor...