101 lines
2.8 KiB
C
101 lines
2.8 KiB
C
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/**********************************************************************
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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) 2021 Paul Ramsey <pramsey@cleverelephant.ca>
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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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#pragma once
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#include <geos/export.h>
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#include <memory>
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// Forward declarations
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namespace geos {
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namespace geom {
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class Geometry;
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}
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}
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using geos::geom::Geometry;
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namespace geos { // geos.
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namespace operation { // geos.operation
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namespace overlayng { // geos.operation.overlayng
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/**
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* Unions a valid coverage of polygons or lines
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* in an efficient way.
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*
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* A valid polygonal coverage is a collection of geom::Polygon
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* which satisfy the following conditions:
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*
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* * Vector-clean - Line segments within the collection
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* must either be identical or intersect only at endpoints.
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* * Non-overlapping - No two polygons
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* may overlap. Equivalently, polygons must be interior-disjoint.
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*
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* A valid linear coverage is a collection of geom::LineString
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* which satisfies the Vector-clean condition.
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* Note that this does not require the LineStrings to be fully noded
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* - i.e. they may contain coincident linework.
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* Coincident line segments are dissolved by the union.
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* Currently linear output is not merged (this may be added in a future release.)
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*
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* Currently no checking is done to determine whether the input is a valid coverage.
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* This is because coverage validation involves segment intersection detection,
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* which is much more expensive than the union phase.
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* If the input is not a valid coverage
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* then in some cases this will be detected during processing
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* and a util::TopologyException is thrown.
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* Otherwise, the computation will produce output, but it will be invalid.
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*
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* Unioning a valid coverage implies that no new vertices are created.
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* This means that a precision model does not need to be specified.
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* The precision of the vertices in the output geometry is not changed.
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*
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* @author Martin Davis
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*
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* @see noding::SegmentExtractingNoder
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*
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*/
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class GEOS_DLL CoverageUnion {
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private:
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CoverageUnion()
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{
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// No instantiation for now
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};
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public:
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static constexpr double AREA_PCT_DIFF_TOL = 1e-6;
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/**
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* Unions a valid polygonal coverage or linear network.
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*
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* @param coverage a coverage of polygons or lines
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* @return the union of the coverage
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*
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* @throws util::TopologyException in some cases if the coverage is invalid
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*/
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static std::unique_ptr<Geometry> geomunion(const Geometry* coverage);
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};
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} // namespace geos.operation.overlayng
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} // namespace geos.operation
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} // namespace geos
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