RingClipper.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2020 Paul Ramsey <pramsey@cleverelephant.ca>
 *
 * 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.
 *
 **********************************************************************/
 
#pragma once
 
#include <geos/export.h>
 
#include <geos/geom/Envelope.h>
#include <geos/geom/CoordinateSequence.h>
 
// Forward declarations
namespace geos {
namespace geom {
class Coordinate;
class CoordinateSequence;
}
}
 
namespace geos {      // geos.
namespace operation { // geos.operation
namespace overlayng { // geos.operation.overlayng
 
class GEOS_DLL RingClipper {
    using Coordinate = geos::geom::Coordinate;
    using CoordinateXY = geos::geom::CoordinateXY;
    using CoordinateSequence = geos::geom::CoordinateSequence;
    using Envelope = geos::geom::Envelope;
 
private:
 
    // Constants
    static constexpr int BOX_LEFT = 3;
    static constexpr int BOX_TOP = 2;
    static constexpr int BOX_RIGHT = 1;
    static constexpr int BOX_BOTTOM = 0;
 
    // Members
    const Envelope clipEnv;
 
    // Methods
 
    std::unique_ptr<CoordinateSequence> clipToBoxEdge(const CoordinateSequence* pts, int edgeIndex, bool closeRing) const;
 
    void intersection(const CoordinateXY& a, const CoordinateXY& b, int edgeIndex, CoordinateXY& rsltPt) const;
    static double intersectionLineY(const CoordinateXY& a, const CoordinateXY& b, double y);
    static double intersectionLineX(const CoordinateXY& a, const CoordinateXY& b, double x);
    bool isInsideEdge(const CoordinateXY& p, int edgeIndex) const;
 
 
public:
 
    RingClipper(const Envelope* env)
        : clipEnv(*env)
        {};
 
    std::unique_ptr<CoordinateSequence> clip(const CoordinateSequence* cs) const;
 
};
 
 
} // namespace geos.operation.overlayng
} // namespace geos.operation
} // namespace geos