QGIS API Documentation  3.4.15-Madeira (e83d02e274)
qgsalgorithmshortestpathlayertopoint.cpp
Go to the documentation of this file.
1 /***************************************************************************
2  qgsalgorithmshortestpathlayertopoint.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 
22 #include "qgsmessagelog.h"
23 
25 
26 QString QgsShortestPathLayerToPointAlgorithm::name() const
27 {
28  return QStringLiteral( "shortestpathlayertopoint" );
29 }
30 
31 QString QgsShortestPathLayerToPointAlgorithm::displayName() const
32 {
33  return QObject::tr( "Shortest path (layer to point)" );
34 }
35 
36 QStringList QgsShortestPathLayerToPointAlgorithm::tags() const
37 {
38  return QObject::tr( "network,path,shortest,fastest" ).split( ',' );
39 }
40 
41 QString QgsShortestPathLayerToPointAlgorithm::shortHelpString() const
42 {
43  return QObject::tr( "This algorithm computes optimal (shortest or fastest) route from multiple start points defined by vector layer and given end point." );
44 }
45 
46 QgsShortestPathLayerToPointAlgorithm *QgsShortestPathLayerToPointAlgorithm::createInstance() const
47 {
48  return new QgsShortestPathLayerToPointAlgorithm();
49 }
50 
51 void QgsShortestPathLayerToPointAlgorithm::initAlgorithm( const QVariantMap & )
52 {
53  addCommonParams();
54  addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "START_POINTS" ), QObject::tr( "Vector layer with start points" ), QList< int >() << QgsProcessing::TypeVectorPoint ) );
55  addParameter( new QgsProcessingParameterPoint( QStringLiteral( "END_POINT" ), QObject::tr( "End point" ) ) );
56 
57  addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Shortest path" ), QgsProcessing::TypeVectorLine ) );
58 }
59 
60 QVariantMap QgsShortestPathLayerToPointAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
61 {
62  loadCommonParams( parameters, context, feedback );
63 
64  QgsPointXY endPoint = parameterAsPoint( parameters, QStringLiteral( "END_POINT" ), context, mNetwork->sourceCrs() );
65 
66  std::unique_ptr< QgsFeatureSource > startPoints( parameterAsSource( parameters, QStringLiteral( "START_POINTS" ), context ) );
67  if ( !startPoints )
68  throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "START_POINTS" ) ) );
69 
70  QgsFields fields = startPoints->fields();
71  fields.append( QgsField( QStringLiteral( "start" ), QVariant::String ) );
72  fields.append( QgsField( QStringLiteral( "end" ), QVariant::String ) );
73  fields.append( QgsField( QStringLiteral( "cost" ), QVariant::Double ) );
74 
75  QString dest;
76  std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, fields, QgsWkbTypes::LineString, mNetwork->sourceCrs() ) );
77  if ( !sink )
78  throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
79 
80  QVector< QgsPointXY > points;
81  points.push_front( endPoint );
82  QHash< int, QgsAttributes > sourceAttributes;
83  loadPoints( startPoints.get(), points, sourceAttributes, context, feedback );
84 
85  feedback->pushInfo( QObject::tr( "Building graph…" ) );
86  QVector< QgsPointXY > snappedPoints;
87  mDirector->makeGraph( mBuilder.get(), points, snappedPoints, feedback );
88 
89  feedback->pushInfo( QObject::tr( "Calculating shortest paths…" ) );
90  QgsGraph *graph = mBuilder->graph();
91  int idxEnd = graph->findVertex( snappedPoints[0] );
92  int idxStart;
93  int currentIdx;
94 
95  QVector< int > tree;
96  QVector< double > costs;
97 
98  QVector<QgsPointXY> route;
99  double cost;
100 
101  QgsFeature feat;
102  feat.setFields( fields );
103  QgsAttributes attributes;
104 
105  int step = points.size() > 0 ? 100.0 / points.size() : 1;
106  for ( int i = 1; i < points.size(); i++ )
107  {
108  if ( feedback->isCanceled() )
109  {
110  break;
111  }
112 
113  idxStart = graph->findVertex( snappedPoints[i] );
114  QgsGraphAnalyzer::dijkstra( graph, idxStart, 0, &tree, &costs );
115 
116  if ( tree.at( idxEnd ) == -1 )
117  {
118  feedback->reportError( QObject::tr( "There is no route from start point (%1) to end point (%2)." )
119  .arg( points[i].toString(),
120  endPoint.toString() ) );
121  feat.clearGeometry();
122  attributes = sourceAttributes.value( i );
123  attributes.append( points[i].toString() );
124  feat.setAttributes( attributes );
125  sink->addFeature( feat, QgsFeatureSink::FastInsert );
126  continue;
127  }
128 
129  route.clear();
130  route.push_front( graph->vertex( idxEnd ).point() );
131  cost = costs.at( idxEnd );
132  currentIdx = idxEnd;
133  while ( currentIdx != idxStart )
134  {
135  currentIdx = graph->edge( tree.at( currentIdx ) ).fromVertex();
136  route.push_front( graph->vertex( currentIdx ).point() );
137  }
138 
140  QgsFeature feat;
141  feat.setFields( fields );
142  attributes = sourceAttributes.value( i );
143  attributes.append( points[i].toString() );
144  attributes.append( endPoint.toString() );
145  attributes.append( cost / mMultiplier );
146  feat.setAttributes( attributes );
147  feat.setGeometry( geom );
148  sink->addFeature( feat, QgsFeatureSink::FastInsert );
149 
150  feedback->setProgress( i * step );
151  }
152 
153  QVariantMap outputs;
154  outputs.insert( QStringLiteral( "OUTPUT" ), dest );
155  return outputs;
156 }
157 
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition: qgsfeedback.h:54
Use faster inserts, at the cost of updating the passed features to reflect changes made at the provid...
static QgsGeometry fromPolylineXY(const QgsPolylineXY &polyline)
Creates a new LineString geometry from a list of QgsPointXY points.
Base class for providing feedback from a processing algorithm.
void setFields(const QgsFields &fields, bool initAttributes=false)
Assign a field map with the feature to allow attribute access by attribute name.
Definition: qgsfeature.cpp:162
A class to represent a 2D point.
Definition: qgspointxy.h:43
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition: qgsfeedback.h:63
Container of fields for a vector layer.
Definition: qgsfields.h:42
QgsPointXY point() const
Returns point associated with graph vertex.
Definition: qgsgraph.cpp:114
A geometry is the spatial representation of a feature.
Definition: qgsgeometry.h:106
void setAttributes(const QgsAttributes &attrs)
Sets the feature&#39;s attributes.
Definition: qgsfeature.cpp:127
int findVertex(const QgsPointXY &pt) const
Find vertex by associated point.
Definition: qgsgraph.cpp:65
The feature class encapsulates a single feature including its id, geometry and a list of field/values...
Definition: qgsfeature.h:55
QString toString(int precision=-1) const
Returns a string representation of the point (x, y) with a preset precision.
Definition: qgspointxy.cpp:40
A feature sink output for processing algorithms.
const QgsGraphEdge & edge(int idx) const
Returns edge at given index.
Definition: qgsgraph.cpp:50
Custom exception class for processing related exceptions.
Definition: qgsexception.h:82
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
Encapsulate a field in an attribute table or data source.
Definition: qgsfield.h:48
Mathematical graph representation.
Definition: qgsgraph.h:141
void clearGeometry()
Removes any geometry associated with the feature.
Definition: qgsfeature.cpp:151
A point parameter for processing algorithms.
Vector point layers.
Definition: qgsprocessing.h:48
An input feature source (such as vector layers) parameter for processing algorithms.
Vector line layers.
Definition: qgsprocessing.h:49
void setGeometry(const QgsGeometry &geometry)
Set the feature&#39;s geometry.
Definition: qgsfeature.cpp:137
const QgsGraphVertex & vertex(int idx) const
Returns vertex at given index.
Definition: qgsgraph.cpp:45
A vector of attributes.
Definition: qgsattributes.h:57
Contains information about the context in which a processing algorithm is executed.
virtual void reportError(const QString &error, bool fatalError=false)
Reports that the algorithm encountered an error while executing.
virtual void pushInfo(const QString &info)
Pushes a general informational message from the algorithm.
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.