QGIS API Documentation 3.34.0-Prizren (ffbdd678812)
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qgsalgorithmextractvertices.cpp
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1/***************************************************************************
2 qgsalgorithmextractvertices.cpp
3 --------------------------
4 begin : November 2017
5 copyright : (C) 2017 by Mathieu Pellerin
6 email : nirvn dot asia 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 "qgsabstractgeometry.h"
21#include "qgsgeometryutils.h"
22
24
25QString QgsExtractVerticesAlgorithm::name() const
26{
27 return QStringLiteral( "extractvertices" );
28}
29
30QString QgsExtractVerticesAlgorithm::displayName() const
31{
32 return QObject::tr( "Extract vertices" );
33}
34
35QStringList QgsExtractVerticesAlgorithm::tags() const
36{
37 return QObject::tr( "points,vertex,nodes" ).split( ',' );
38}
39
40QString QgsExtractVerticesAlgorithm::group() const
41{
42 return QObject::tr( "Vector geometry" );
43}
44
45QString QgsExtractVerticesAlgorithm::groupId() const
46{
47 return QStringLiteral( "vectorgeometry" );
48}
49
50QString QgsExtractVerticesAlgorithm::shortHelpString() const
51{
52 return QObject::tr( "This algorithm takes a line or polygon layer and generates a point layer with points representing the vertices in the input lines or polygons. The attributes associated to each point are the same ones associated to the line or polygon that the point belongs to." ) +
53 QStringLiteral( "\n\n" ) +
54 QObject::tr( "Additional fields are added to the point indicating the vertex index (beginning at 0), the vertex’s part and its index within the part (as well as its ring for polygons), distance along original geometry and bisector angle of vertex for original geometry." );
55}
56
57QString QgsExtractVerticesAlgorithm::outputName() const
58{
59 return QObject::tr( "Vertices" );
60}
61
62QgsExtractVerticesAlgorithm *QgsExtractVerticesAlgorithm::createInstance() const
63{
64 return new QgsExtractVerticesAlgorithm();
65}
66
67QgsProcessing::SourceType QgsExtractVerticesAlgorithm::outputLayerType() const
68{
70}
71
72QgsFields QgsExtractVerticesAlgorithm::outputFields( const QgsFields &inputFields ) const
73{
74 QgsFields outputFields = inputFields;
75 outputFields.append( QgsField( QStringLiteral( "vertex_index" ), QVariant::Int, QString(), 10, 0 ) );
76 outputFields.append( QgsField( QStringLiteral( "vertex_part" ), QVariant::Int, QString(), 10, 0 ) );
77 if ( mGeometryType == Qgis::GeometryType::Polygon )
78 {
79 outputFields.append( QgsField( QStringLiteral( "vertex_part_ring" ), QVariant::Int, QString(), 10, 0 ) );
80 }
81 outputFields.append( QgsField( QStringLiteral( "vertex_part_index" ), QVariant::Int, QString(), 10, 0 ) );
82 outputFields.append( QgsField( QStringLiteral( "distance" ), QVariant::Double, QString(), 20, 14 ) );
83 outputFields.append( QgsField( QStringLiteral( "angle" ), QVariant::Double, QString(), 20, 14 ) );
84
85 return outputFields;
86}
87
88Qgis::WkbType QgsExtractVerticesAlgorithm::outputWkbType( Qgis::WkbType inputWkbType ) const
89{
90 Qgis::WkbType outputWkbType = Qgis::WkbType::Point;
91 if ( QgsWkbTypes::hasM( inputWkbType ) )
92 {
93 outputWkbType = QgsWkbTypes::addM( outputWkbType );
94 }
95 if ( QgsWkbTypes::hasZ( inputWkbType ) )
96 {
97 outputWkbType = QgsWkbTypes::addZ( outputWkbType );
98 }
99
100 return outputWkbType;
101}
102
103QgsProcessingFeatureSource::Flag QgsExtractVerticesAlgorithm::sourceFlags() const
104{
106}
107
108QgsFeatureSink::SinkFlags QgsExtractVerticesAlgorithm::sinkFlags() const
109{
111}
112
113bool QgsExtractVerticesAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
114{
115 std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
116 mGeometryType = QgsWkbTypes::geometryType( source->wkbType() );
117 return true;
118}
119
120QgsFeatureList QgsExtractVerticesAlgorithm::processFeature( const QgsFeature &feature, QgsProcessingContext &, QgsProcessingFeedback * )
121{
122 QgsFeatureList outputFeatures;
123
124 QgsFeature f = feature;
125 const QgsGeometry inputGeom = f.geometry();
126 if ( inputGeom.isNull() )
127 {
128 QgsAttributes attrs = f.attributes();
129 attrs << QVariant()
130 << QVariant();
131 if ( mGeometryType == Qgis::GeometryType::Polygon )
132 {
133 attrs << QVariant();
134 }
135 attrs << QVariant()
136 << QVariant()
137 << QVariant();
138
139 f.setAttributes( attrs );
140 outputFeatures << f;
141 }
142 else
143 {
145 double cumulativeDistance = 0.0;
146 int vertexPos = 0;
147 while ( vi != inputGeom.constGet()->vertices_end() )
148 {
149 const QgsVertexId vertexId = vi.vertexId();
150 const double angle = inputGeom.constGet()->vertexAngle( vertexId ) * 180 / M_PI;
151 QgsAttributes attrs = f.attributes();
152 attrs << vertexPos
153 << vertexId.part;
154 if ( mGeometryType == Qgis::GeometryType::Polygon )
155 {
156 attrs << vertexId.ring;
157 }
158 attrs << vertexId.vertex
159 << cumulativeDistance
160 << angle;
161
162 QgsFeature outputFeature = QgsFeature();
163 outputFeature.setAttributes( attrs );
164 outputFeature.setGeometry( QgsGeometry( ( *vi ).clone() ) );
165 outputFeatures << outputFeature;
166 vi++;
167 vertexPos++;
168
169 // calculate distance to next vertex
170 const double distanceToNext = inputGeom.constGet()->segmentLength( vertexId );
171 cumulativeDistance += distanceToNext;
172 }
173 }
174
175 return outputFeatures;
176}
177
@ Polygon
Polygons.
WkbType
The WKB type describes the number of dimensions a geometry has.
Definition qgis.h:182
The vertex_iterator class provides STL-style iterator for vertices.
QgsVertexId vertexId() const
Returns vertex ID of the current item.
virtual double vertexAngle(QgsVertexId vertex) const =0
Returns approximate angle at a vertex.
vertex_iterator vertices_end() const
Returns STL-style iterator pointing to the imaginary vertex after the last vertex of the geometry.
vertex_iterator vertices_begin() const
Returns STL-style iterator pointing to the first vertex of the geometry.
virtual double segmentLength(QgsVertexId startVertex) const =0
Returns the length of the segment of the geometry which begins at startVertex.
A vector of attributes.
@ 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:56
QgsAttributes attributes
Definition qgsfeature.h:65
void setAttributes(const QgsAttributes &attrs)
Sets the feature's attributes.
QgsGeometry geometry
Definition qgsfeature.h:67
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:45
bool append(const QgsField &field, FieldOrigin origin=OriginProvider, int originIndex=-1)
Appends a field. The field must have unique name, otherwise it is rejected (returns false)
Definition qgsfields.cpp:59
A geometry is the spatial representation of a feature.
const QgsAbstractGeometry * constGet() const
Returns a non-modifiable (const) reference to the underlying abstract geometry primitive.
Contains information about the context in which a processing algorithm is executed.
Flag
Flags controlling how QgsProcessingFeatureSource fetches features.
@ FlagSkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
Base class for providing feedback from a processing algorithm.
SourceType
Data source types enum.
@ TypeVectorPoint
Vector point layers.
static Qgis::GeometryType geometryType(Qgis::WkbType type)
Returns the geometry type for a WKB type, e.g., both MultiPolygon and CurvePolygon would have a Polyg...
static Qgis::WkbType addM(Qgis::WkbType type)
Adds the m dimension to a WKB type and returns the new type.
static Qgis::WkbType addZ(Qgis::WkbType type)
Adds the z dimension to a WKB type and returns the new type.
static bool hasZ(Qgis::WkbType type)
Tests whether a WKB type contains the z-dimension.
static bool hasM(Qgis::WkbType type)
Tests whether a WKB type contains m values.
double ANALYSIS_EXPORT angle(QgsPoint *p1, QgsPoint *p2, QgsPoint *p3, QgsPoint *p4)
Calculates the angle between two segments (in 2 dimension, z-values are ignored)
QList< QgsFeature > QgsFeatureList
Definition qgsfeature.h:920
Utility class for identifying a unique vertex within a geometry.
Definition qgsvertexid.h:31
int vertex
Vertex number.
Definition qgsvertexid.h:95
int part
Part number.
Definition qgsvertexid.h:89
int ring
Ring number.
Definition qgsvertexid.h:92