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geos-3.7.3/include/geos/operation/overlay/snap/LineStringSnapper.h  view on Meta::CPAN

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2009-2010  Sandro Santilli <strk@kbt.io>
 * Copyright (C) 2006 Refractions Research Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 ***********************************************************************
 *
 * Last port: operation/overlay/snap/LineStringSnapper.java r320 (JTS-1.12)
 *
 **********************************************************************/

#ifndef GEOS_OP_OVERLAY_SNAP_LINESTRINGSNAPPER_H
#define GEOS_OP_OVERLAY_SNAP_LINESTRINGSNAPPER_H

#include <geos/geom/Coordinate.h>
#include <geos/geom/CoordinateSequence.h>
#include <geos/geom/CoordinateList.h>

#include <memory>

// Forward declarations
namespace geos {
	namespace geom {
		//class PrecisionModel;
		//class CoordinateSequence;
		class CoordinateList;
		class Geometry;
	}
}

namespace geos {
namespace operation { // geos::operation
namespace overlay { // geos::operation::overlay
namespace snap { // geos::operation::overlay::snap

/** \brief
 * Snaps the vertices and segments of a LineString to a set
 * of target snap vertices.
 *
 * A snapping distance tolerance is used to control where snapping is performed.
 *
 */
class GEOS_DLL LineStringSnapper {

public:

	/**
	 * Creates a new snapper using the given points
	 * as source points to be snapped.
	 *
	 * @param nSrcPts the points to snap
	 * @param nSnapTolerance the snap tolerance to use
	 */
	LineStringSnapper(const geom::Coordinate::Vect& nSrcPts,
	                                          double nSnapTol)
		:
		srcPts(nSrcPts),
		snapTolerance(nSnapTol),
		allowSnappingToSourceVertices(false)
	{
		size_t s = srcPts.size();
		isClosed = s < 2 ? false : srcPts[0].equals2D(srcPts[s-1]);
	}

	// Snap points are assumed to be all distinct points (a set would be better, uh ?)
	std::unique_ptr<geom::Coordinate::Vect> snapTo(const geom::Coordinate::ConstVect& snapPts);

	void setAllowSnappingToSourceVertices(bool allow) {
		allowSnappingToSourceVertices = allow;
	}

private:

	const geom::Coordinate::Vect& srcPts;

	double snapTolerance;

	bool allowSnappingToSourceVertices;
	bool isClosed;


	// Modifies first arg
	void snapVertices(geom::CoordinateList& srcCoords,
			const geom::Coordinate::ConstVect& snapPts);


	// Returns snapPts.end() if no snap point is close enough (within snapTol distance)
	geom::Coordinate::ConstVect::const_iterator findSnapForVertex(const geom::Coordinate& pt,
			const geom::Coordinate::ConstVect& snapPts);

  /** \brief
   * Snap segments of the source to nearby snap vertices.
   *
   * Source segments are "cracked" at a snap vertex.
   * A single input segment may be snapped several times
   * to different snap vertices.
   *
   * For each distinct snap vertex, at most one source segment
   * is snapped to.  This prevents "cracking" multiple segments
   * at the same point, which would likely cause
   * topology collapse when being used on polygonal linework.
   *
   * @param srcCoords the coordinates of the source linestring to be snapped
   *                  the object will be modified (coords snapped)
   * @param snapPts the target snap vertices                                       */
  void snapSegments(geom::CoordinateList& srcCoords,
                    const geom::Coordinate::ConstVect& snapPts);

	/// \brief
	/// Finds a src segment which snaps to (is close to) the given snap
	/// point.
	//
	/// Only a single segment is selected for snapping.
	/// This prevents multiple segments snapping to the same snap vertex,
	/// which would almost certainly cause invalid geometry
	/// to be created.
	/// (The heuristic approach to snapping used here
	/// is really only appropriate when
	/// snap pts snap to a unique spot on the src geometry.)
	///
	/// Also, if the snap vertex occurs as a vertex in the src
	/// coordinate list, no snapping is performed (may be changed
	/// using setAllowSnappingToSourceVertices).
	///
	/// @param from
	///        an iterator to first point of first segment to be checked
	///
	/// @param too_far
	///        an iterator to last point of last segment to be checked
	///
	/// @returns an iterator to the snapped segment or
	///          too_far if no segment needs snapping
	///          (either none within snapTol distance,
	///           or one found on the snapPt)
	///
	geom::CoordinateList::iterator findSegmentToSnap(
			const geom::Coordinate& snapPt,
			geom::CoordinateList::iterator from,
			geom::CoordinateList::iterator too_far);

	geom::CoordinateList::iterator findVertexToSnap(
			const geom::Coordinate& snapPt,
			geom::CoordinateList::iterator from,
			geom::CoordinateList::iterator too_far);

    // Declare type as noncopyable
    LineStringSnapper(const LineStringSnapper& other) = delete;
    LineStringSnapper& operator=(const LineStringSnapper& rhs) = delete;
};


} // namespace geos::operation::overlay::snap
} // namespace geos::operation::overlay
} // namespace geos::operation
} // namespace geos

#endif // GEOS_OP_OVERLAY_SNAP_LINESTRINGSNAPPER_H