308 lines
9.2 KiB
C
308 lines
9.2 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) 2009-2011 Sandro Santilli <strk@kbt.io>
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* Copyright (C) 2005-2007 Refractions Research Inc.
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* Copyright (C) 2001-2002 Vivid Solutions Inc.
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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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*
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* Last port: operation/buffer/BufferOp.java r378 (JTS-1.12)
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*
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**********************************************************************/
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#pragma once
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#include <memory> // for unique_ptr
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#include <vector> // for vector
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#include <geos/export.h>
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#include <geos/operation/buffer/BufferParameters.h> // for enum values
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#include <geos/geom/Geometry.h> // to materialize Geometry
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#include <geos/util/TopologyException.h> // for composition
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#ifdef _MSC_VER
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#pragma warning(push)
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#pragma warning(disable: 4251) // warning C4251: needs to have dll-interface to be used by clients of class
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#endif
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// Forward declarations
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namespace geos {
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namespace geom {
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class PrecisionModel;
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class Geometry;
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}
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}
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namespace geos {
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namespace operation { // geos.operation
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namespace buffer { // geos.operation.buffer
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/**
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* \class BufferOp
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*
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* \brief
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* Computes the buffer of a geometry, for both positive and negative
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* buffer distances.
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*
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* In GIS, the positive (or negative) buffer of a geometry is defined as
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* the Minkowski sum (or difference) of the geometry
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* with a circle with radius equal to the absolute value of the buffer
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* distance.
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* In the CAD/CAM world buffers are known as *offset curves*.
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* In morphological analysis the operation of positive and negative buffering
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* is referred to as *erosion* and *dilation*.
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*
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* The buffer operation always returns a polygonal result.
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* The negative or zero-distance buffer of lines and points is always
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* an empty Polygon.
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*
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* Since true buffer curves may contain circular arcs,
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* computed buffer polygons can only be approximations to the true geometry.
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* The user can control the accuracy of the curve approximation by specifying
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* the number of linear segments with which to approximate a curve.
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*
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* The end cap style of a linear buffer may be specified.
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* The following end cap styles are supported:
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* - CAP_ROUND - the usual round end caps
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* - CAP_BUTT - end caps are truncated flat at the line ends
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* - CAP_SQUARE - end caps are squared off at the buffer distance
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* beyond the line ends
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*
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*/
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class GEOS_DLL BufferOp {
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private:
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/** \brief
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* A number of digits of precision which leaves some computational "headroom"
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* for floating point operations.
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*
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* This value should be less than the decimal precision of double-precision values (16).
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*/
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static constexpr int MAX_PRECISION_DIGITS = 12;
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const geom::Geometry* argGeom;
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util::TopologyException saveException;
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double distance;
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BufferParameters bufParams;
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std::unique_ptr<geom::Geometry> resultGeometry;
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bool isInvertOrientation = false;
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/**
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* Compute a reasonable scale factor to limit the precision of
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* a given combination of Geometry and buffer distance.
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* The scale factor is based on a heuristic.
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*
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* @param g the Geometry being buffered
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*
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* @param distance the buffer distance
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*
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* @param maxPrecisionDigits the mzx # of digits that should be
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* allowed by the precision determined by the
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* computed scale factor
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*
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* @return a scale factor that allows a reasonable amount of
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* precision for the buffer computation
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*/
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static double precisionScaleFactor(const geom::Geometry* g,
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double distance, int maxPrecisionDigits);
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void computeGeometry();
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void bufferOriginalPrecision();
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void bufferReducedPrecision(int precisionDigits);
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void bufferReducedPrecision();
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void bufferFixedPrecision(const geom::PrecisionModel& fixedPM);
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static void extractPolygons(
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geom::Geometry* poly0,
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std::vector<std::unique_ptr<geom::Geometry>>& polys);
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public:
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enum {
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/// Specifies a round line buffer end cap style.
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/// @deprecated use BufferParameters
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CAP_ROUND = BufferParameters::CAP_ROUND,
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/// Specifies a butt (or flat) line buffer end cap style.
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/// @deprecated use BufferParameters
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CAP_BUTT = BufferParameters::CAP_FLAT,
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/// Specifies a square line buffer end cap style.
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/// @deprecated use BufferParameters
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CAP_SQUARE = BufferParameters::CAP_SQUARE
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};
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/** \brief
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* Computes the buffer for a geometry for a given buffer distance
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* and accuracy of approximation.
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*
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* @param g the geometry to buffer
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* @param distance the buffer distance
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* @param quadrantSegments the number of segments used to
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* approximate a quarter circle
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* @param endCapStyle line buffer end cap style (default: BufferParameters::CAP_ROUND)
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* @return the buffer of the input geometry
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*
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*/
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static std::unique_ptr<geom::Geometry> bufferOp(
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const geom::Geometry* g,
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double distance,
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int quadrantSegments = BufferParameters::DEFAULT_QUADRANT_SEGMENTS,
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int endCapStyle = BufferParameters::CAP_ROUND);
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static std::unique_ptr<geom::Geometry> bufferOp(
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const geom::Geometry* g,
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double distance,
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BufferParameters& bufParms);
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/** \brief
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* Initializes a buffer computation for the given geometry.
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*
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* @param g the geometry to buffer
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*/
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BufferOp(const geom::Geometry* g)
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:
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argGeom(g),
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bufParams(),
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resultGeometry(nullptr),
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isInvertOrientation(false)
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{
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}
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/** \brief
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* Initializes a buffer computation for the given geometry
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* with the given set of parameters.
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*
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* @param g the geometry to buffer
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* @param params the buffer parameters to use. This class will
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* copy it to private memory.
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*/
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BufferOp(const geom::Geometry* g, const BufferParameters& params)
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:
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argGeom(g),
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bufParams(params),
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resultGeometry(nullptr),
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isInvertOrientation(false)
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{
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}
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/** \brief
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* Specifies the end cap style of the generated buffer.
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*
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* The styles supported are CAP_ROUND, CAP_BUTT, and CAP_SQUARE.
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* The default is CAP_ROUND.
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*
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* @param nEndCapStyle the end cap style to specify
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*/
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inline void setEndCapStyle(int nEndCapStyle);
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/** \brief
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* Sets the number of segments used to approximate a angle fillet
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*
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* @param nQuadrantSegments the number of segments in a fillet for a quadrant
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*/
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inline void setQuadrantSegments(int nQuadrantSegments);
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/** \brief
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* Sets whether the computed buffer should be single-sided.
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*
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* A single-sided buffer is constructed on only one side
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* of each input line.
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*
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* The side used is determined by the sign of the buffer distance:
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* - a positive distance indicates the left-hand side
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* - a negative distance indicates the right-hand side
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*
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* The single-sided buffer of point geometries is
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* the same as the regular buffer.
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*
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* The End Cap Style for single-sided buffers is
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* always ignored,
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* and forced to the equivalent of `CAP_FLAT`.
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*
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* @param isSingleSided `true` if a single-sided buffer
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* should be constructed
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*/
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inline void setSingleSided(bool isSingleSided);
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/** \brief
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* Returns the buffer computed for a geometry for a given buffer
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* distance.
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*
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* @param nDistance the buffer distance
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* @return the buffer of the input geometry
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*/
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std::unique_ptr<geom::Geometry> getResultGeometry(double nDistance);
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/**
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* Buffers a geometry with distance zero.
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* The result can be computed using the maximum-signed-area orientation,
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* or by combining both orientations.
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*
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* This can be used to fix an invalid polygonal geometry to be valid
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* (i.e. with no self-intersections).
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* For some uses (e.g. fixing the result of a simplification)
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* a better result is produced by using only the max-area orientation.
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* Other uses (e.g. fixing geometry) require both orientations to be used.
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*
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* This function is for INTERNAL use only.
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*
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* @param geom the polygonal geometry to buffer by zero
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* @param isBothOrientations true if both orientations of input rings should be used
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* @return the buffered polygonal geometry
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*/
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static std::unique_ptr<geom::Geometry> bufferByZero(
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const geom::Geometry* geom,
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bool isBothOrientations);
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};
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// BufferOp inlines
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void
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BufferOp::setQuadrantSegments(int q)
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{
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bufParams.setQuadrantSegments(q);
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}
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void
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BufferOp::setEndCapStyle(int s)
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{
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bufParams.setEndCapStyle((BufferParameters::EndCapStyle)s);
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}
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void
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BufferOp::setSingleSided(bool isSingleSided)
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{
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bufParams.setSingleSided(isSingleSided);
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}
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} // namespace geos::operation::buffer
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} // namespace geos::operation
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} // namespace geos
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#ifdef _MSC_VER
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#pragma warning(pop)
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#endif
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