QGIS API Documentation 3.34.0-Prizren (ffbdd678812)
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qgsalgorithmshortestpathpointtopoint.cpp
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1/***************************************************************************
2 qgsalgorithmshortestpathpointtopoint.cpp
3 ---------------------
4 begin : July 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
20#include "qgsgraphanalyzer.h"
21
23
24QString QgsShortestPathPointToPointAlgorithm::name() const
25{
26 return QStringLiteral( "shortestpathpointtopoint" );
27}
28
29QString QgsShortestPathPointToPointAlgorithm::displayName() const
30{
31 return QObject::tr( "Shortest path (point to point)" );
32}
33
34QStringList QgsShortestPathPointToPointAlgorithm::tags() const
35{
36 return QObject::tr( "network,path,shortest,fastest" ).split( ',' );
37}
38
39QString QgsShortestPathPointToPointAlgorithm::shortHelpString() const
40{
41 return QObject::tr( "This algorithm computes optimal (shortest or fastest) route between given start and end points." );
42}
43
44QgsShortestPathPointToPointAlgorithm *QgsShortestPathPointToPointAlgorithm::createInstance() const
45{
46 return new QgsShortestPathPointToPointAlgorithm();
47}
48
49void QgsShortestPathPointToPointAlgorithm::initAlgorithm( const QVariantMap & )
50{
51 addCommonParams();
52 addParameter( new QgsProcessingParameterPoint( QStringLiteral( "START_POINT" ), QObject::tr( "Start point" ) ) );
53 addParameter( new QgsProcessingParameterPoint( QStringLiteral( "END_POINT" ), QObject::tr( "End point" ) ) );
54
55 addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Shortest path" ), QgsProcessing::TypeVectorLine ) );
56 addOutput( new QgsProcessingOutputNumber( QStringLiteral( "TRAVEL_COST" ), QObject::tr( "Travel cost" ) ) );
57}
58
59QVariantMap QgsShortestPathPointToPointAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
60{
61 loadCommonParams( parameters, context, feedback );
62
63 QgsFields fields;
64 fields.append( QgsField( QStringLiteral( "start" ), QVariant::String ) );
65 fields.append( QgsField( QStringLiteral( "end" ), QVariant::String ) );
66 fields.append( QgsField( QStringLiteral( "cost" ), QVariant::Double ) );
67
68 QString dest;
69 std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, fields, Qgis::WkbType::LineString, mNetwork->sourceCrs() ) );
70 if ( !sink )
71 throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
72
73 const QgsPointXY startPoint = parameterAsPoint( parameters, QStringLiteral( "START_POINT" ), context, mNetwork->sourceCrs() );
74 const QgsPointXY endPoint = parameterAsPoint( parameters, QStringLiteral( "END_POINT" ), context, mNetwork->sourceCrs() );
75
76 feedback->pushInfo( QObject::tr( "Building graph…" ) );
77 QVector< QgsPointXY > points;
78 points << startPoint << endPoint;
79 QVector< QgsPointXY > snappedPoints;
80 mDirector->makeGraph( mBuilder.get(), points, snappedPoints, feedback );
81
82 feedback->pushInfo( QObject::tr( "Calculating shortest path…" ) );
83 std::unique_ptr< QgsGraph > graph( mBuilder->takeGraph() );
84 const int idxStart = graph->findVertex( snappedPoints[0] );
85 int idxEnd = graph->findVertex( snappedPoints[1] );
86
87 QVector< int > tree;
88 QVector< double > costs;
89 QgsGraphAnalyzer::dijkstra( graph.get(), idxStart, 0, &tree, &costs );
90
91 if ( tree.at( idxEnd ) == -1 )
92 {
93 throw QgsProcessingException( QObject::tr( "There is no route from start point to end point." ) );
94 }
95
96 QVector<QgsPointXY> route;
97 route.push_front( graph->vertex( idxEnd ).point() );
98 const double cost = costs.at( idxEnd );
99 while ( idxEnd != idxStart )
100 {
101 idxEnd = graph->edge( tree.at( idxEnd ) ).fromVertex();
102 route.push_front( graph->vertex( idxEnd ).point() );
103 }
104
105 feedback->pushInfo( QObject::tr( "Writing results…" ) );
106 const QgsGeometry geom = QgsGeometry::fromPolylineXY( route );
107 QgsFeature feat;
108 feat.setFields( fields );
109 QgsAttributes attributes;
110 attributes << startPoint.toString() << endPoint.toString() << cost / mMultiplier;
111 feat.setGeometry( geom );
112 feat.setAttributes( attributes );
113 if ( !sink->addFeature( feat, QgsFeatureSink::FastInsert ) )
114 throw QgsProcessingException( writeFeatureError( sink.get(), parameters, QStringLiteral( "OUTPUT" ) ) );
115
116 QVariantMap outputs;
117 outputs.insert( QStringLiteral( "OUTPUT" ), dest );
118 outputs.insert( QStringLiteral( "TRAVEL_COST" ), cost / mMultiplier );
119 return outputs;
120}
121
@ LineString
LineString.
A vector of attributes.
@ 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:56
void setAttributes(const QgsAttributes &attrs)
Sets the feature's attributes.
void setFields(const QgsFields &fields, bool initAttributes=false)
Assigns a field map with the feature to allow attribute access by attribute name.
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.
static QgsGeometry fromPolylineXY(const QgsPolylineXY &polyline)
Creates a new LineString geometry from a list of QgsPointXY points.
static void dijkstra(const QgsGraph *source, int startVertexIdx, int criterionNum, QVector< int > *resultTree=nullptr, QVector< double > *resultCost=nullptr)
Solve shortest path problem using Dijkstra algorithm.
A class to represent a 2D point.
Definition qgspointxy.h:59
QString toString(int precision=-1) const
Returns a string representation of the point (x, y) with a preset precision.
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.
A numeric output for processing algorithms.
A feature sink output for processing algorithms.
A point parameter for processing algorithms.
@ TypeVectorLine
Vector line layers.