QGIS API Documentation 3.39.0-Master (67e056379ed)
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qgsalgorithmpolygonize.cpp
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1/***************************************************************************
2 qgsalgorithmdpolygonize.cpp
3 ---------------------
4 begin : May 2020
5 copyright : (C) 2020 by Alexander Bruy
6 email : alexander dot bruy 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
20
22
23QString QgsPolygonizeAlgorithm::name() const
24{
25 return QStringLiteral( "polygonize" );
26}
27
28QString QgsPolygonizeAlgorithm::displayName() const
29{
30 return QObject::tr( "Polygonize" );
31}
32
33QString QgsPolygonizeAlgorithm::shortHelpString() const
34{
35 return QObject::tr( "Creates a polygon layer from the input lines layer." );
36}
37
38QStringList QgsPolygonizeAlgorithm::tags() const
39{
40 return QObject::tr( "create,lines,polygons,convert" ).split( ',' );
41}
42
43QString QgsPolygonizeAlgorithm::group() const
44{
45 return QObject::tr( "Vector geometry" );
46}
47
48QString QgsPolygonizeAlgorithm::groupId() const
49{
50 return QStringLiteral( "vectorgeometry" );
51}
52
53void QgsPolygonizeAlgorithm::initAlgorithm( const QVariantMap & )
54{
55 addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ),
56 QObject::tr( "Input layer" ), QList< int >() << static_cast< int >( Qgis::ProcessingSourceType::VectorLine ) ) );
57 addParameter( new QgsProcessingParameterBoolean( QStringLiteral( "KEEP_FIELDS" ),
58 QObject::tr( "Keep table structure of line layer" ), false, true ) );
59 addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ),
60 QObject::tr( "Polygons" ), Qgis::ProcessingSourceType::VectorPolygon ) );
61 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "NUM_POLYGONS" ), QObject::tr( "Number of polygons" ) ) );
62}
63
64QgsPolygonizeAlgorithm *QgsPolygonizeAlgorithm::createInstance() const
65{
66 return new QgsPolygonizeAlgorithm();
67}
68
69QVariantMap QgsPolygonizeAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
70{
71 std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
72 if ( !source )
73 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
74
75 QgsFields fields = QgsFields();
76 if ( parameterAsBoolean( parameters, QStringLiteral( "KEEP_FIELDS" ), context ) )
77 fields = source->fields();
78
79 QString dest;
80 std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, fields, Qgis::WkbType::Polygon, source->sourceCrs() ) );
81 if ( !sink )
82 throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
83
84 int polygonCount = 0;
85
86 feedback->pushInfo( QObject::tr( "Collecting lines…" ) );
87 const int i = 0;
88 double step = source->featureCount() > 0 ? 40.0 / source->featureCount() : 1;
89 QgsFeature f;
90 QgsFeatureIterator features = source->getFeatures( QgsFeatureRequest().setNoAttributes() );
91 QVector<QgsGeometry> linesList;
92 linesList.reserve( source->featureCount() );
93 while ( features.nextFeature( f ) )
94 {
95 if ( feedback->isCanceled() )
96 break;
97
98 if ( f.hasGeometry() )
99 linesList << f.geometry();
100
101 feedback->setProgress( i * step );
102 }
103 feedback->setProgress( 40 );
104
105 feedback->pushInfo( QObject::tr( "Noding lines…" ) );
106 const QgsGeometry lines = QgsGeometry::unaryUnion( linesList );
107 if ( feedback->isCanceled() )
108 return QVariantMap();
109 feedback->setProgress( 45 );
110
111 feedback->pushInfo( QObject::tr( "Polygonizing…" ) );
112 const QgsGeometry polygons = QgsGeometry::polygonize( QVector< QgsGeometry >() << lines );
113 if ( polygons.isEmpty() )
114 feedback->reportError( QObject::tr( "No polygons were created." ) );
115
116 feedback->setProgress( 50 );
117
118 if ( !polygons.isEmpty() )
119 {
120 const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( polygons.constGet() );
121 step = collection->numGeometries() > 0 ? 50.0 / collection->numGeometries() : 1;
122 for ( int part = 0; part < collection->numGeometries(); ++part )
123 {
124 if ( feedback->isCanceled() )
125 break;
126
127 QgsFeature outFeat;
128 outFeat.setGeometry( QgsGeometry( collection->geometryN( part )->clone() ) );
129 if ( !sink->addFeature( outFeat, QgsFeatureSink::FastInsert ) )
130 throw QgsProcessingException( writeFeatureError( sink.get(), parameters, QStringLiteral( "OUTPUT" ) ) );
131 feedback->setProgress( 50 + i * step );
132 polygonCount += 1;
133 }
134 }
135
136 QVariantMap outputs;
137 outputs.insert( QStringLiteral( "OUTPUT" ), dest );
138 outputs.insert( QStringLiteral( "NUM_POLYGONS" ), polygonCount );
139 return outputs;
140}
141
@ VectorPolygon
Vector polygon layers.
@ VectorLine
Vector line layers.
@ Polygon
Polygon.
virtual QgsAbstractGeometry * clone() const =0
Clones the geometry by performing a deep copy.
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).
@ FastInsert
Use faster inserts, at the cost of updating the passed features to reflect changes made at the provid...
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:58
QgsGeometry geometry
Definition qgsfeature.h:69
bool hasGeometry() const
Returns true if the feature has an associated geometry.
void setGeometry(const QgsGeometry &geometry)
Set the feature's geometry.
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
Container of fields for a vector layer.
Definition qgsfields.h:46
int numGeometries() const
Returns the number of geometries within the collection.
const QgsAbstractGeometry * geometryN(int n) const
Returns a const reference to a geometry from within the collection.
A geometry is the spatial representation of a feature.
static QgsGeometry polygonize(const QVector< QgsGeometry > &geometries)
Creates a GeometryCollection geometry containing possible polygons formed from the constituent linewo...
const QgsAbstractGeometry * constGet() const
Returns a non-modifiable (const) reference to the underlying abstract geometry primitive.
bool isEmpty() const
Returns true if the geometry is empty (eg a linestring with no vertices, or a collection with no geom...
static QgsGeometry unaryUnion(const QVector< QgsGeometry > &geometries, const QgsGeometryParameters &parameters=QgsGeometryParameters())
Compute the unary union on a list of geometries.
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.
A numeric output for processing algorithms.
A boolean parameter for processing algorithms.
A feature sink output for processing algorithms.
An input feature source (such as vector layers) parameter for processing algorithms.