296 lines
9.0 KiB
C++
296 lines
9.0 KiB
C++
/**********************************************************************
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*
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* GEOS - Geometry Engine Open Source
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* http://geos.osgeo.org
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*
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* Copyright (C) 2011 Sandro Santilli <strk@kbt.io>
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* Copyright (C) 2006 Refractions Research Inc.
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*
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* This is free software; you can redistribute and/or modify it under
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* the terms of the GNU Lesser General Public Licence as published
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* by the Free Software Foundation.
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* See the COPYING file for more information.
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*
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**********************************************************************
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*
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* Last port: operation/linemerge/LineSequencer.java r378 (JTS-1.12)
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*
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**********************************************************************/
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#pragma once
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#include <geos/export.h>
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#include <geos/operation/linemerge/LineMergeGraph.h> // for composition
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#include <geos/geom/Geometry.h> // for inlines
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#include <geos/geom/LineString.h> // for inlines
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#include <vector>
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#include <list>
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#include <memory> // for unique_ptr
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#ifdef _MSC_VER
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#pragma warning(push)
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#pragma warning(disable: 4251) // warning C4251: needs to have dll-interface to be used by clients of class
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#endif
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// Forward declarations
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namespace geos {
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namespace geom {
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class GeometryFactory;
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class Geometry;
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class LineString;
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}
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namespace planargraph {
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class DirectedEdge;
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class Subgraph;
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class Node;
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}
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}
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namespace geos {
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namespace operation { // geos::operation
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namespace linemerge { // geos::operation::linemerge
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/** \brief
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* Builds a sequence from a set of LineStrings so that
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* they are ordered end to end.
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*
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* A sequence is a complete non-repeating list of the linear
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* components of the input. Each linestring is oriented
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* so that identical endpoints are adjacent in the list.
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*
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* A typical use case is to convert a set of unoriented geometric links
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* from a linear network (e.g. such as block faces on a bus route)
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* into a continuous oriented path through the network.
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*
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* The input linestrings may form one or more connected sets.
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* The input linestrings should be correctly noded, or the results may
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* not be what is expected.
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* The computed output is a single MultiLineString containing the ordered
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* linestrings in the sequence.
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*
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* The sequencing employs the classic **Eulerian path** graph algorithm.
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* Since Eulerian paths are not uniquely determined, further rules are used
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* to make the computed sequence preserve as much as possible of the input
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* ordering. Within a connected subset of lines, the ordering rules are:
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*
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* - If there is degree-1 node which is the start
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* node of an linestring, use that node as the start of the sequence
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* - If there is a degree-1 node which is the end
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* node of an linestring, use that node as the end of the sequence
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* - If the sequence has no degree-1 nodes, use any node as the start
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*
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* @note Not all arrangements of lines can be sequenced. For a connected
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* set of edges in a graph, *Euler's Theorem* states that there is a sequence
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* containing each edge once **if and only if** there are no more than
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* 2 nodes of odd degree. If it is not possible to find a sequence, the
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* `isSequenceable` method will return `false`.
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*
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*/
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class GEOS_DLL LineSequencer {
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private:
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typedef std::list<planargraph::DirectedEdge*> DirEdgeList;
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typedef std::vector< DirEdgeList* > Sequences;
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LineMergeGraph graph;
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const geom::GeometryFactory* factory;
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unsigned int lineCount;
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bool isRun;
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std::unique_ptr<geom::Geometry> sequencedGeometry;
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bool isSequenceableVar;
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void addLine(const geom::LineString* lineString);
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void computeSequence();
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Sequences* findSequences();
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DirEdgeList* findSequence(planargraph::Subgraph& graph);
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void delAll(Sequences&);
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/**
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* Builds a geometry ({@link LineString} or {@link MultiLineString} )
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* representing the sequence.
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*
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* @param sequences
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* a vector of vectors of const planarDirectedEdges
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* with LineMergeEdges as their parent edges.
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* Ownership of container _and_ contents retained by caller.
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*
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* @return the sequenced geometry, possibly NULL
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* if no sequence exists
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*/
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geom::Geometry* buildSequencedGeometry(const Sequences& sequences);
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static const planargraph::Node* findLowestDegreeNode(
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const planargraph::Subgraph& graph);
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void addReverseSubpath(const planargraph::DirectedEdge* de,
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DirEdgeList& deList,
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DirEdgeList::iterator lit,
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bool expectedClosed);
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/**
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* Finds an {@link DirectedEdge} for an unvisited edge (if any),
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* choosing the dirEdge which preserves orientation, if possible.
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*
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* @param node the node to examine
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* @return the dirEdge found, or <code>null</code>
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* if none were unvisited
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*/
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static const planargraph::DirectedEdge* findUnvisitedBestOrientedDE(
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const planargraph::Node* node);
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/**
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* Computes a version of the sequence which is optimally
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* oriented relative to the underlying geometry.
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*
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* Heuristics used are:
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*
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* - If the path has a degree-1 node which is the start
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* node of an linestring, use that node as the start of the sequence
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* - If the path has a degree-1 node which is the end
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* node of an linestring, use that node as the end of the sequence
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* - If the sequence has no degree-1 nodes, use any node as the start
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* (NOTE: in this case could orient the sequence according to the
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* majority of the linestring orientations)
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*
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* @param seq a List of planarDirectedEdges
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* @return the oriented sequence, possibly same as input if already
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* oriented
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*/
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DirEdgeList* orient(DirEdgeList* seq);
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/**
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* Reverse the sequence.
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* This requires reversing the order of the dirEdges, and flipping
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* each dirEdge as well
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*
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* @param seq a List of DirectedEdges, in sequential order
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* @return the reversed sequence
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*/
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DirEdgeList* reverse(DirEdgeList& seq);
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/**
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* Tests whether a complete unique path exists in a graph
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* using Euler's Theorem.
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*
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* @param graph the subgraph containing the edges
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* @return <code>true</code> if a sequence exists
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*/
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bool hasSequence(planargraph::Subgraph& graph);
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public:
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static geom::Geometry*
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sequence(const geom::Geometry& geom)
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{
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LineSequencer sequencer;
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sequencer.add(geom);
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return sequencer.getSequencedLineStrings();
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}
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LineSequencer()
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:
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factory(nullptr),
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lineCount(0),
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isRun(false),
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sequencedGeometry(nullptr),
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isSequenceableVar(false)
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{}
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/** \brief
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* Tests whether a [Geometry](@ref geom::Geometry) is sequenced correctly.
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*
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* [LineStrings](@ref geom::LineString) are trivially sequenced.
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* [MultiLineStrings](@ref geom::MultiLineString) are checked for
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* correct sequencing. Otherwise, `isSequenced` is defined
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* to be `true` for geometries that are not lineal.
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*
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* @param geom the geometry to test
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* @return `true` if the geometry is sequenced or is not lineal
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*/
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static bool isSequenced(const geom::Geometry* geom);
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/** \brief
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* Tests whether the arrangement of linestrings has a valid
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* sequence.
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*
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* @return `true` if a valid sequence exists.
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*/
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bool
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isSequenceable()
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{
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computeSequence();
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return isSequenceableVar;
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}
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/** \brief
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* Adds a [Geometry](@ref geom::Geometry) to be sequenced.
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*
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* May be called multiple times.
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* Any dimension of Geometry may be added; the constituent
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* linework will be extracted.
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*
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* @param geometry the geometry to add
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*/
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void
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add(const geom::Geometry& geometry)
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{
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geometry.applyComponentFilter(*this);
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}
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template <class TargetContainer>
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void
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add(TargetContainer& geoms)
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{
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for(typename TargetContainer::const_iterator i = geoms.begin(),
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e = geoms.end(); i != e; ++i) {
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const geom::Geometry* g = *i;
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add(*g);
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}
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}
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/** \brief
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* Act as a GeometryComponentFilter so to extract
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* the linearworks
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*/
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void
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filter(const geom::Geometry* g)
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{
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if(const geom::LineString* ls = dynamic_cast<const geom::LineString*>(g)) {
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addLine(ls);
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}
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}
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/** \brief
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* Returns the LineString or MultiLineString
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* built by the sequencing process, if one exists.
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*
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* @param release release ownership of computed Geometry
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* @return the sequenced linestrings,
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* or `null` if a valid sequence
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* does not exist.
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*/
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geom::Geometry*
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getSequencedLineStrings(bool release = 1)
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{
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computeSequence();
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if(release) {
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return sequencedGeometry.release();
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}
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else {
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return sequencedGeometry.get();
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}
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}
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};
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} // namespace geos::operation::linemerge
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} // namespace geos::operation
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} // namespace geos
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#ifdef _MSC_VER
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#pragma warning(pop)
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#endif
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