113 lines
3.2 KiB
C++
113 lines
3.2 KiB
C++
/**********************************************************************
|
|
*
|
|
* 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;
|
|
}
|
|
}
|
|
|
|
using namespace geos::geom;
|
|
|
|
namespace geos { // geos.
|
|
namespace operation { // geos.operation
|
|
namespace overlayng { // geos.operation.overlayng
|
|
|
|
/**
|
|
* Clips rings of points to a rectangle.
|
|
* Uses a variant of Cohen-Sutherland clipping.
|
|
*
|
|
* In general the output is not topologically valid.
|
|
* In particular, the output may contain coincident non-noded line segments
|
|
* along the clip rectangle sides.
|
|
* However, the output is sufficiently well-structured
|
|
* that it can be used as input to the {@link OverlayNG} algorithm
|
|
* (which is able to process coincident linework due
|
|
* to the need to handle topology collapse under precision reduction).
|
|
*
|
|
* Because of the likelihood of creating
|
|
* extraneous line segments along the clipping rectangle sides,
|
|
* this class is not suitable for clipping linestrings.
|
|
*
|
|
* The clipping envelope should be generated using {@link RobustClipEnvelopeComputer},
|
|
* to ensure that intersecting line segments are not perturbed
|
|
* by clipping.
|
|
* This is required to ensure that the overlay of the
|
|
* clipped geometry is robust and correct (i.e. the same as
|
|
* if clipping was not used).
|
|
*
|
|
* @see LineLimiter
|
|
*
|
|
* @author Martin Davis
|
|
*
|
|
*/
|
|
class GEOS_DLL RingClipper {
|
|
|
|
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
|
|
|
|
/**
|
|
* Clips line to the axis-parallel line defined by a single box edge.
|
|
*/
|
|
std::unique_ptr<CoordinateSequence> clipToBoxEdge(const CoordinateSequence* pts, int edgeIndex, bool closeRing) const;
|
|
|
|
/**
|
|
* Computes the intersection point of a segment
|
|
* with an edge of the clip box.
|
|
* The segment must be known to intersect the edge.
|
|
*/
|
|
void intersection(const Coordinate& a, const Coordinate& b, int edgeIndex, Coordinate& rsltPt) const;
|
|
double intersectionLineY(const Coordinate& a, const Coordinate& b, double y) const;
|
|
double intersectionLineX(const Coordinate& a, const Coordinate& b, double x) const;
|
|
bool isInsideEdge(const Coordinate& p, int edgeIndex) const;
|
|
|
|
|
|
public:
|
|
|
|
RingClipper(const Envelope* env)
|
|
: clipEnv(*env)
|
|
{};
|
|
|
|
/**
|
|
* Clips a list of points to the clipping rectangle box.
|
|
*/
|
|
std::unique_ptr<CoordinateSequence> clip(const CoordinateSequence* cs) const;
|
|
|
|
};
|
|
|
|
|
|
} // namespace geos.operation.overlayng
|
|
} // namespace geos.operation
|
|
} // namespace geos
|
|
|