OffsetCurve.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2021 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/operation/buffer/BufferParameters.h>
#include <geos/geom/GeometryFactory.h>
#include <geos/constants.h>
 
// Forward declarations
namespace geos {
namespace geom {
class Coordinate;
class CoordinateSequence;
class Geometry;
class LineString;
class Polygon;
}
namespace operation {
namespace buffer {
class OffsetCurveSection;
class SegmentMCIndex;
}
}
}
 
namespace geos {
namespace operation {
namespace buffer {

class GEOS_DLL OffsetCurve {
    using Coordinate = geos::geom::Coordinate;
    using CoordinateSequence = geos::geom::CoordinateSequence;
    using Geometry = geos::geom::Geometry;
    using GeometryFactory = geos::geom::GeometryFactory;
    using LineString = geos::geom::LineString;
    using Polygon = geos::geom::Polygon;
 
private:
 
    // Members
    const Geometry& inputGeom;
    double distance;
    bool isJoined = false;
 
    BufferParameters bufferParams;
    double matchDistance;
    const GeometryFactory* geomFactory;
 
    // Methods
 
    std::unique_ptr<Geometry> computePolygonCurve(
        const Polygon& polyGeom, double distance);
 
    std::unique_ptr<Geometry> computeCurve(
        const LineString& lineGeom, double distance);
 
    std::vector<std::unique_ptr<OffsetCurveSection>> computeSections(
        const LineString& lineGeom, double distance);
 
    std::unique_ptr<LineString> offsetSegment(
        const CoordinateSequence* pts, double distance);
 
    static std::unique_ptr<Polygon> getBufferOriented(
        const LineString& geom, double distance,
        BufferParameters& bufParams);

    static const Polygon* extractMaxAreaPolygon(const Geometry* geom);
 
    void computeCurveSections(
        const CoordinateSequence* bufferRingPts,
        const CoordinateSequence& rawCurve,
        std::vector<std::unique_ptr<OffsetCurveSection>>& sections);

    std::size_t matchSegments(
        const Coordinate& raw0, const Coordinate& raw1,
        std::size_t rawCurveIndex,
        SegmentMCIndex& bufferSegIndex,
        const CoordinateSequence* bufferPts,
        std::vector<double>& rawCurvePos);
 
    static double segmentMatchFrac(
        const Coordinate& p0,   const Coordinate& p1,
        const Coordinate& seg0, const Coordinate& seg1,
        double matchDistance);

    void extractSections(
        const CoordinateSequence* ringPts,
        std::vector<double>& rawCurveLoc,
        std::size_t startIndex,
        std::vector<std::unique_ptr<OffsetCurveSection>>& sections);
 
    std::size_t findSectionStart(
        const std::vector<double>& loc,
        std::size_t end);
 
    std::size_t findSectionEnd(
        const std::vector<double>& loc,
        std::size_t start,
        std::size_t firstStartIndex);
 
    static std::size_t nextIndex(std::size_t i, std::size_t size);
    static std::size_t prevIndex(std::size_t i, std::size_t size);
 
 
public:
 
    // Constants
    static constexpr int MATCH_DISTANCE_FACTOR = 10000;

    static constexpr int MIN_QUADRANT_SEGMENTS = 8;

    OffsetCurve(const Geometry& geom, double dist)
        : inputGeom(geom)
        , distance(dist)
        , matchDistance(std::abs(dist)/MATCH_DISTANCE_FACTOR)
        , geomFactory(geom.getFactory())
        {
            if (!std::isfinite(dist)) {
                throw util::IllegalArgumentException("OffsetCurve distance must be a finite value");
            }
        };

    OffsetCurve(const Geometry& geom, double dist, BufferParameters& bp)
        : inputGeom(geom)
        , distance(dist)
        , matchDistance(std::abs(dist)/MATCH_DISTANCE_FACTOR)
        , geomFactory(geom.getFactory())
        {
            if (!std::isfinite(dist)) {
                throw util::IllegalArgumentException("OffsetCurve distance must be a finite value");
            }
            //-- set buffer params, leaving cap style as the default CAP_ROUND

            int quadSegs = bp.getQuadrantSegments();
            if (quadSegs < MIN_QUADRANT_SEGMENTS) {
                quadSegs = MIN_QUADRANT_SEGMENTS;
            }
            bufferParams.setQuadrantSegments(quadSegs);
 
            bufferParams.setJoinStyle( bp.getJoinStyle());
            bufferParams.setMitreLimit( bp.getMitreLimit());
        };

    void setJoined(bool pIsJoined);
 
    static std::unique_ptr<Geometry> getCurve(
        const Geometry& geom,
        double dist,
        int quadSegs,
        BufferParameters::JoinStyle joinStyle,
        double mitreLimit);
 
    static std::unique_ptr<Geometry> getCurve(
        const Geometry& geom, double dist);

    static std::unique_ptr<Geometry> getCurveJoined(
        const Geometry& geom, double dist);

    std::unique_ptr<Geometry> getCurve();

    static std::unique_ptr<CoordinateSequence> rawOffsetCurve(
        const LineString& line,
        double distance,
        BufferParameters& bufParams);

    static std::unique_ptr<CoordinateSequence> rawOffset(
        const LineString& line,
        double distance);
 
};
 
} // namespace geos::operation::buffer
} // namespace geos::operation
} // namespace geos