QGIS API Documentation 3.40.0-Bratislava (b56115d8743)
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qgsalgorithmmultiunion.cpp
Go to the documentation of this file.
1/***************************************************************************
2 qgsalgorithmmultiunion.cpp
3 ------------------
4 begin : December 2021
5 copyright : (C) 2021 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
19
20#include "qgsoverlayutils.h"
21#include "qgsvectorlayer.h"
22
24
25
26QString QgsMultiUnionAlgorithm::name() const
27{
28 return QStringLiteral( "multiunion" );
29}
30
31QString QgsMultiUnionAlgorithm::displayName() const
32{
33 return QObject::tr( "Union (multiple)" );
34}
35
36QStringList QgsMultiUnionAlgorithm::tags() const
37{
38 return QObject::tr( "union,overlap,not overlap" ).split( ',' );
39}
40
41QString QgsMultiUnionAlgorithm::group() const
42{
43 return QObject::tr( "Vector overlay" );
44}
45
46QString QgsMultiUnionAlgorithm::groupId() const
47{
48 return QStringLiteral( "vectoroverlay" );
49}
50
51QString QgsMultiUnionAlgorithm::shortHelpString() const
52{
53 return QObject::tr( "This algorithm checks overlaps between features within the Input layer and creates separate features for overlapping "
54 "and non-overlapping parts. The area of overlap will create as many identical overlapping features as there are "
55 "features that participate in that overlap." )
56 + QStringLiteral( "\n\n" )
57 + QObject::tr( "Multiple Overlay layers can also be used, in which case features from each layer are split at their overlap with features from "
58 "all other layers, creating a layer containing all the portions from both Input and Overlay layers. "
59 "The attribute table of the Union layer is filled with attribute values from the respective original layer "
60 "for non-overlapping features, and attribute values from both layers for overlapping features." );
61}
62
63Qgis::ProcessingAlgorithmDocumentationFlags QgsMultiUnionAlgorithm::documentationFlags() const
64{
66}
67
68QgsProcessingAlgorithm *QgsMultiUnionAlgorithm::createInstance() const
69{
70 return new QgsMultiUnionAlgorithm();
71}
72
73void QgsMultiUnionAlgorithm::initAlgorithm( const QVariantMap & )
74{
75 addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ) ) );
76 addParameter( new QgsProcessingParameterMultipleLayers( QStringLiteral( "OVERLAYS" ), QObject::tr( "Overlay layers" ), Qgis::ProcessingSourceType::VectorAnyGeometry, QVariant(), true ) );
77
78 std::unique_ptr< QgsProcessingParameterString > prefix = std::make_unique< QgsProcessingParameterString >( QStringLiteral( "OVERLAY_FIELDS_PREFIX" ), QObject::tr( "Overlay fields prefix" ), QString(), false, true );
79 prefix->setFlags( prefix->flags() | Qgis::ProcessingParameterFlag::Advanced );
80 addParameter( prefix.release() );
81
82 addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Union" ) ) );
83}
84
85QVariantMap QgsMultiUnionAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
86{
87 std::unique_ptr< QgsFeatureSource > sourceA( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
88 if ( !sourceA )
89 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
90
91 const QList< QgsMapLayer * > layers = parameterAsLayerList( parameters, QStringLiteral( "OVERLAYS" ), context );
92
93 // loop through overlay layers and check whether they are vectors
94 long totalLayerCount = 0;
95 for ( QgsMapLayer *layer : layers )
96 {
97 if ( feedback->isCanceled() )
98 break;
99
100 if ( !layer )
101 throw QgsProcessingException( QObject::tr( "Error retrieving map layer." ) );
102
103 if ( layer->type() != Qgis::LayerType::Vector )
104 throw QgsProcessingException( QObject::tr( "All layers must be vector layers!" ) );
105
106 totalLayerCount++;
107 }
108
109 const Qgis::WkbType geometryType = QgsWkbTypes::multiType( sourceA->wkbType() );
110 const QgsCoordinateReferenceSystem crs = sourceA->sourceCrs();
111 const QString overlayFieldsPrefix = parameterAsString( parameters, QStringLiteral( "OVERLAY_FIELDS_PREFIX" ), context );
112 std::unique_ptr< QgsFeatureSink > sink;
113 QVariantMap outputs;
114 bool ok;
115
116 if ( totalLayerCount == 0 )
117 {
118 // we are doing single layer union
119 QString dest;
120 std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, sourceA->fields(), geometryType, sourceA->sourceCrs(), QgsFeatureSink::RegeneratePrimaryKey ) );
121 if ( !sink )
122 throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
123
124 outputs.insert( QStringLiteral( "OUTPUT" ), dest );
125
126 QgsOverlayUtils::resolveOverlaps( *sourceA, *sink, feedback );
127 return outputs;
128 }
129 else
130 {
131 QgsProcessingMultiStepFeedback multiStepFeedback( totalLayerCount, feedback );
132 QgsVectorLayer *unionLayer = nullptr;
133 QgsFields fields;
134
135 long i = 0;
136 for ( QgsMapLayer *layer : layers )
137 {
138 if ( feedback->isCanceled() )
139 break;
140
141 multiStepFeedback.setCurrentStep( i );
142
143 if ( !layer )
144 continue;
145
146 QgsVectorLayer *overlayLayer = qobject_cast< QgsVectorLayer * >( layer );
147 if ( !overlayLayer )
148 continue;
149
150 if ( i == 0 )
151 {
152 QString id = QStringLiteral( "memory:" );
153 fields = QgsProcessingUtils::combineFields( sourceA->fields(), overlayLayer->fields(), overlayFieldsPrefix );
154 sink.reset( QgsProcessingUtils::createFeatureSink( id, context, fields, geometryType, crs, QVariantMap(), QStringList(), QStringList(), QgsFeatureSink::RegeneratePrimaryKey ) );
155 ok = makeUnion( *sourceA, *overlayLayer, *sink, context, &multiStepFeedback );
156
157 if ( !ok )
158 throw QgsProcessingException( QObject::tr( "Interrupted by user." ) );
159
160 unionLayer = qobject_cast< QgsVectorLayer * >( QgsProcessingUtils::mapLayerFromString( id, context ) );
161 }
162 else if ( i == totalLayerCount - 1 )
163 {
164 fields = QgsProcessingUtils::combineFields( unionLayer->fields(), overlayLayer->fields(), overlayFieldsPrefix );
165
166
167 QString dest;
168 std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, fields, geometryType, crs, QgsFeatureSink::RegeneratePrimaryKey ) );
169 if ( !sink )
170 throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
171
172 outputs.insert( QStringLiteral( "OUTPUT" ), dest );
173 ok = makeUnion( *unionLayer, *overlayLayer, *sink, context, &multiStepFeedback );
174 if ( !ok )
175 throw QgsProcessingException( QObject::tr( "Interrupted by user." ) );
176 }
177 else
178 {
179 QString id = QStringLiteral( "memory:" );
180 fields = QgsProcessingUtils::combineFields( unionLayer->fields(), overlayLayer->fields(), overlayFieldsPrefix );
181 sink.reset( QgsProcessingUtils::createFeatureSink( id, context, fields, geometryType, crs, QVariantMap(), QStringList(), QStringList(), QgsFeatureSink::RegeneratePrimaryKey ) );
182 ok = makeUnion( *unionLayer, *overlayLayer, *sink, context, &multiStepFeedback );
183 if ( !ok )
184 throw QgsProcessingException( QObject::tr( "Interrupted by user." ) );
185
186 unionLayer = qobject_cast< QgsVectorLayer * >( QgsProcessingUtils::mapLayerFromString( id, context ) );
187 }
188
189 i++;
190 }
191 }
192
193 return outputs;
194}
195
196bool QgsMultiUnionAlgorithm::makeUnion( const QgsFeatureSource &sourceA, const QgsFeatureSource &sourceB, QgsFeatureSink &sink, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
197{
198 const QList<int> fieldIndicesA = QgsProcessingUtils::fieldNamesToIndices( QStringList(), sourceA.fields() );
199 const QList<int> fieldIndicesB = QgsProcessingUtils::fieldNamesToIndices( QStringList(), sourceB.fields() );
200
201 long count = 0;
202 const long total = sourceA.featureCount() * 2 + sourceB.featureCount();
203
204 QgsOverlayUtils::intersection( sourceA, sourceB, sink, context, feedback, count, total, fieldIndicesA, fieldIndicesB );
205 if ( feedback->isCanceled() )
206 return false;
207
208 QgsOverlayUtils::difference( sourceA, sourceB, sink, context, feedback, count, total, QgsOverlayUtils::OutputAB );
209 if ( feedback->isCanceled() )
210 return false;
211
212 QgsOverlayUtils::difference( sourceB, sourceA, sink, context, feedback, count, total, QgsOverlayUtils::OutputBA );
213 return true;
214}
215
@ VectorAnyGeometry
Any vector layer with geometry.
@ RegeneratesPrimaryKey
Algorithm always drops any existing primary keys or FID values and regenerates them in outputs.
@ Vector
Vector layer.
QFlags< ProcessingAlgorithmDocumentationFlag > ProcessingAlgorithmDocumentationFlags
Flags describing algorithm behavior for documentation purposes.
Definition qgis.h:3359
WkbType
The WKB type describes the number of dimensions a geometry has.
Definition qgis.h:256
@ Advanced
Parameter is an advanced parameter which should be hidden from users by default.
This class represents a coordinate reference system (CRS).
An interface for objects which accept features via addFeature(s) methods.
@ RegeneratePrimaryKey
This flag indicates, that a primary key field cannot be guaranteed to be unique and the sink should i...
An interface for objects which provide features via a getFeatures method.
virtual QgsFields fields() const =0
Returns the fields associated with features in the source.
virtual long long featureCount() const =0
Returns the number of features contained in the source, or -1 if the feature count is unknown.
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition qgsfeedback.h:53
Container of fields for a vector layer.
Definition qgsfields.h:46
Base class for all map layer types.
Definition qgsmaplayer.h:76
Abstract base class for processing algorithms.
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.
Processing feedback object for multi-step operations.
A feature sink output for processing algorithms.
An input feature source (such as vector layers) parameter for processing algorithms.
A parameter for processing algorithms which accepts multiple map layers.
static QList< int > fieldNamesToIndices(const QStringList &fieldNames, const QgsFields &fields)
Returns a list of field indices parsed from the given list of field names.
static QgsFields combineFields(const QgsFields &fieldsA, const QgsFields &fieldsB, const QString &fieldsBPrefix=QString())
Combines two field lists, avoiding duplicate field names (in a case-insensitive manner).
static QgsFeatureSink * createFeatureSink(QString &destination, QgsProcessingContext &context, const QgsFields &fields, Qgis::WkbType geometryType, const QgsCoordinateReferenceSystem &crs, const QVariantMap &createOptions=QVariantMap(), const QStringList &datasourceOptions=QStringList(), const QStringList &layerOptions=QStringList(), QgsFeatureSink::SinkFlags sinkFlags=QgsFeatureSink::SinkFlags(), QgsRemappingSinkDefinition *remappingDefinition=nullptr)
Creates a feature sink ready for adding features.
static QgsMapLayer * mapLayerFromString(const QString &string, QgsProcessingContext &context, bool allowLoadingNewLayers=true, QgsProcessingUtils::LayerHint typeHint=QgsProcessingUtils::LayerHint::UnknownType, QgsProcessing::LayerOptionsFlags flags=QgsProcessing::LayerOptionsFlags())
Interprets a string as a map layer within the supplied context.
Represents a vector layer which manages a vector based data sets.
static Qgis::WkbType multiType(Qgis::WkbType type)
Returns the multi type for a WKB type.
const QgsCoordinateReferenceSystem & crs