QGIS API Documentation 3.39.0-Master (67e056379ed)
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qgsalgorithmmultiringconstantbuffer.cpp
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1/***************************************************************************
2 qgsalgorithmnultitingconstantbuffer.cpp
3 --------------------------
4 begin : February 2018
5 copyright : (C) 2018 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#include "qgsvectorlayer.h"
20
22
23QString QgsMultiRingConstantBufferAlgorithm::name() const
24{
25 return QStringLiteral( "multiringconstantbuffer" );
26}
27
28QString QgsMultiRingConstantBufferAlgorithm::displayName() const
29{
30 return QObject::tr( "Multi-ring buffer (constant distance)" );
31}
32
33QStringList QgsMultiRingConstantBufferAlgorithm::tags() const
34{
35 return QObject::tr( "buffer,grow,multiple,rings,distance,donut" ).split( ',' );
36}
37
38QString QgsMultiRingConstantBufferAlgorithm::group() const
39{
40 return QObject::tr( "Vector geometry" );
41}
42
43QString QgsMultiRingConstantBufferAlgorithm::groupId() const
44{
45 return QStringLiteral( "vectorgeometry" );
46}
47
48QString QgsMultiRingConstantBufferAlgorithm::outputName() const
49{
50 return QObject::tr( "Multi-ring buffer (constant distance)" );
51}
52
53QString QgsMultiRingConstantBufferAlgorithm::shortHelpString() const
54{
55 return QObject::tr( "This algorithm computes multi-ring ('donuts') buffer for all the features in an input layer, using a fixed or dynamic distance and rings number." );
56}
57
58QgsMultiRingConstantBufferAlgorithm *QgsMultiRingConstantBufferAlgorithm::createInstance() const
59{
60 return new QgsMultiRingConstantBufferAlgorithm();
61}
62
63void QgsMultiRingConstantBufferAlgorithm::initParameters( const QVariantMap & )
64{
65 std::unique_ptr< QgsProcessingParameterNumber> rings = std::make_unique< QgsProcessingParameterNumber >( QStringLiteral( "RINGS" ),
66 QObject::tr( "Number of rings" ), Qgis::ProcessingNumberParameterType::Integer,
67 1, false, 0 );
68 rings->setIsDynamic( true );
69 rings->setDynamicPropertyDefinition( QgsPropertyDefinition( QStringLiteral( "RINGS" ), QObject::tr( "Number of rings" ), QgsPropertyDefinition::IntegerPositive ) );
70 rings->setDynamicLayerParameterName( QStringLiteral( "INPUT" ) );
71 addParameter( rings.release() );
72
73 std::unique_ptr< QgsProcessingParameterDistance > distance = std::make_unique< QgsProcessingParameterDistance >( QStringLiteral( "DISTANCE" ),
74 QObject::tr( "Distance between rings" ), 1, QStringLiteral( "INPUT" ), false );
75 distance->setIsDynamic( true );
76 distance->setDynamicPropertyDefinition( QgsPropertyDefinition( QStringLiteral( "DISTANCE" ), QObject::tr( "Distance between rings" ), QgsPropertyDefinition::DoublePositive ) );
77 distance->setDynamicLayerParameterName( QStringLiteral( "INPUT" ) );
78 addParameter( distance.release() );
79}
80
81bool QgsMultiRingConstantBufferAlgorithm::supportInPlaceEdit( const QgsMapLayer *l ) const
82{
83 const QgsVectorLayer *layer = qobject_cast< const QgsVectorLayer * >( l );
84 if ( !layer )
85 return false;
86
88 return false;
89 // Polygons only
90 return layer->wkbType() == Qgis::WkbType::Polygon || layer->wkbType() == Qgis::WkbType::MultiPolygon;
91}
92
93bool QgsMultiRingConstantBufferAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
94{
95 mRingsNumber = parameterAsInt( parameters, QStringLiteral( "RINGS" ), context );
96 mDynamicRingsNumber = QgsProcessingParameters::isDynamic( parameters, QStringLiteral( "RINGS" ) );
97 if ( mDynamicRingsNumber )
98 mRingsNumberProperty = parameters.value( QStringLiteral( "RINGS" ) ).value< QgsProperty >();
99
100 mDistance = parameterAsDouble( parameters, QStringLiteral( "DISTANCE" ), context );
101 mDynamicDistance = QgsProcessingParameters::isDynamic( parameters, QStringLiteral( "DISTANCE" ) );
102 if ( mDynamicDistance )
103 mDistanceProperty = parameters.value( QStringLiteral( "DISTANCE" ) ).value< QgsProperty >();
104
105 return true;
106}
107
108QgsFields QgsMultiRingConstantBufferAlgorithm::outputFields( const QgsFields &inputFields ) const
109{
110 QgsFields fields = inputFields;
111 fields.append( QgsField( QStringLiteral( "ringId" ), QMetaType::Type::Int, QString(), 10, 0 ) );
112 fields.append( QgsField( QStringLiteral( "distance" ), QMetaType::Type::Double, QString(), 20, 6 ) );
113 return fields;
114}
115
116Qgis::ProcessingFeatureSourceFlags QgsMultiRingConstantBufferAlgorithm::sourceFlags() const
117{
119}
120
121QgsFeatureSink::SinkFlags QgsMultiRingConstantBufferAlgorithm::sinkFlags() const
122{
124}
125
126QgsFeatureList QgsMultiRingConstantBufferAlgorithm::processFeature( const QgsFeature &feature, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
127{
128 double currentDistance = 0;
129 QgsGeometry outputGeometry, previousGeometry;
130
131 int rings = mRingsNumber;
132 if ( mDynamicRingsNumber )
133 rings = mRingsNumberProperty.valueAsInt( context.expressionContext(), rings );
134
135 double distance = mDistance;
136 if ( mDynamicDistance )
137 distance = mDistanceProperty.valueAsDouble( context.expressionContext(), distance );
138
139 QgsFeatureList outputs;
140
141 // Set previous geometry to a zero-distance buffer of the original geometry,
142 // this is needed for negative distance values
143 previousGeometry = feature.geometry().buffer( 0.0, 40 );
144 previousGeometry.convertToMultiType();
145
146 for ( int i = 1; i <= rings; ++i )
147 {
148 QgsFeature out;
149 currentDistance = i * distance;
150 outputGeometry = feature.geometry().buffer( currentDistance, 40 );
151 outputGeometry.convertToMultiType();
152 if ( outputGeometry.isNull() )
153 {
154 feedback->reportError( QObject::tr( "Error calculating buffer for feature %1" ).arg( feature.id() ) );
155 continue;
156 }
157
158 if ( distance < 0.0 )
159 {
160 out.setGeometry( previousGeometry.symDifference( outputGeometry ) );
161 }
162 else if ( i == 1 )
163 {
164 out.setGeometry( outputGeometry );
165 }
166 else
167 {
168 out.setGeometry( outputGeometry.symDifference( previousGeometry ) );
169 }
170 previousGeometry = outputGeometry;
171 QgsAttributes attrs = feature.attributes();
172 attrs << i << currentDistance;
173 out.setAttributes( attrs );
174 outputs.append( out );
175 }
176
177 // For negative distance values, the last generated buffer geometry needs to be added
178 if ( distance < 0.0 )
179 {
180 QgsFeature out;
181 out.setGeometry( previousGeometry );
182 QgsAttributes attrs = feature.attributes();
183 attrs << 0 << 0.0;
184 out.setAttributes( attrs );
185 outputs.append( out );
186 }
187
188 return outputs;
189}
190
@ SkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
@ Polygon
Polygon.
@ MultiPolygon
MultiPolygon.
QFlags< ProcessingFeatureSourceFlag > ProcessingFeatureSourceFlags
Flags which control how QgsProcessingFeatureSource fetches features.
Definition qgis.h:3153
A vector of attributes.
QFlags< SinkFlag > SinkFlags
@ RegeneratePrimaryKey
This flag indicates, that a primary key field cannot be guaranteed to be unique and the sink should i...
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:58
QgsAttributes attributes
Definition qgsfeature.h:67
QgsFeatureId id
Definition qgsfeature.h:66
void setAttributes(const QgsAttributes &attrs)
Sets the feature's attributes.
QgsGeometry geometry
Definition qgsfeature.h:69
void setGeometry(const QgsGeometry &geometry)
Set the feature's geometry.
Encapsulate a field in an attribute table or data source.
Definition qgsfield.h:53
Container of fields for a vector layer.
Definition qgsfields.h:46
bool append(const QgsField &field, Qgis::FieldOrigin origin=Qgis::FieldOrigin::Provider, int originIndex=-1)
Appends a field.
Definition qgsfields.cpp:69
A geometry is the spatial representation of a feature.
QgsGeometry symDifference(const QgsGeometry &geometry, const QgsGeometryParameters &parameters=QgsGeometryParameters()) const
Returns a geometry representing the points making up this geometry that do not make up other.
QgsGeometry buffer(double distance, int segments) const
Returns a buffer region around this geometry having the given width and with a specified number of se...
bool convertToMultiType()
Converts single type geometry into multitype geometry e.g.
Base class for all map layer types.
Definition qgsmaplayer.h:75
Contains information about the context in which a processing algorithm is executed.
QgsExpressionContext & expressionContext()
Returns the expression context.
bool supportInPlaceEdit(const QgsMapLayer *layer) const override
Checks whether this algorithm supports in-place editing on the given layer Default implementation for...
Base class for providing feedback from a processing algorithm.
virtual void reportError(const QString &error, bool fatalError=false)
Reports that the algorithm encountered an error while executing.
static bool isDynamic(const QVariantMap &parameters, const QString &name)
Returns true if the parameter with matching name is a dynamic parameter, and must be evaluated once f...
Definition for a property.
Definition qgsproperty.h:45
@ IntegerPositive
Positive integer values (including 0)
Definition qgsproperty.h:53
@ DoublePositive
Positive double value (including 0)
Definition qgsproperty.h:56
A store for object properties.
double valueAsDouble(const QgsExpressionContext &context, double defaultValue=0.0, bool *ok=nullptr) const
Calculates the current value of the property and interprets it as a double.
Represents a vector layer which manages a vector based data sets.
Q_INVOKABLE Qgis::WkbType wkbType() const FINAL
Returns the WKBType or WKBUnknown in case of error.
QList< QgsFeature > QgsFeatureList