geos::operation::buffer::OffsetCurve Class Reference

#include <OffsetCurve.h>

Public Member Functions
	OffsetCurve (const Geometry &geom, double dist)
	OffsetCurve (const Geometry &geom, double dist, BufferParameters &bp)
std::unique_ptr< Geometry >	getCurve ()

Static Public Member Functions
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 void	rawOffset (const LineString &geom, double dist, BufferParameters &bufParams, std::vector< CoordinateSequence * > &lineList)
static void	rawOffset (const LineString &geom, double dist, std::vector< CoordinateSequence * > &lineList)

Detailed Description

Computes an offset curve from a geometry. The offset curve is a linear geometry which is offset a specified distance from the input. If the offset distance is positive the curve lies on the left side of the input; if it is negative the curve is on the right side.

The offset curve of a line is a LineString which The offset curve of a Point is an empty LineString. The offset curve of a Polygon is the boundary of the polygon buffer (which may be a MultiLineString. For a collection the output is a MultiLineString of the element offset curves.

The offset curve is computed as a single contiguous section of the geometry buffer boundary. In some geometric situations this definition is ill-defined. This algorithm provides a "best-effort" interpretation. In particular:

• For self-intersecting lines, the buffer boundary includes offset lines for both left and right sides of the input line. Only a single contiguous portion on the specified side is returned.
• If the offset corresponds to buffer holes, only the largest hole is used.

Offset curves support setting the number of quadrant segments, the join style, and the mitre limit (if applicable) via the BufferParameters.

Author

Martin Davis

Constructor & Destructor Documentation

OffsetCurve() [1/2]

geos::operation::buffer::OffsetCurve::OffsetCurve ( const Geometry &  geom, double  dist  )

inline

Creates a new instance for computing an offset curve for a geometryat a given distance. with default quadrant segments BufferParameters::DEFAULT_QUADRANT_SEGMENTS and join style BufferParameters::JOIN_STYLE.

Parameters

geom	the geometry to offset
dist	the offset distance (positive = left, negative = right)

See also

BufferParameters

OffsetCurve() [2/2]

geos::operation::buffer::OffsetCurve::OffsetCurve ( const Geometry &  geom, double  dist, BufferParameters &  bp  )

inline

Creates a new instance for computing an offset curve for a geometry at a given distance. allowing the quadrant segments and join style and mitre limit to be set via BufferParameters.

Parameters

geom
dist
bp

Member Function Documentation

getCurve()

static std::unique_ptr< Geometry > geos::operation::buffer::OffsetCurve::getCurve ( const Geometry &  geom, double  dist, int  quadSegs, BufferParameters::JoinStyle  joinStyle, double  mitreLimit  )

static

Computes the offset curve of a geometry at a given distance, and for a specified quadrant segments, join style and mitre limit.

Parameters

geom	a geometry
dist	the offset distance (positive = left, negative = right)
quadSegs	the quadrant segments (-1 for default)
joinStyle	the join style (-1 for default)
mitreLimit	the mitre limit (-1 for default)

Returns

the offset curve

rawOffset()

static void geos::operation::buffer::OffsetCurve::rawOffset ( const LineString &  geom, double  dist, BufferParameters &  bufParams, std::vector< CoordinateSequence * > &  lineList  )

static

Gets the raw offset line. The quadrant segments and join style and mitre limit to be set via BufferParameters.

The raw offset line may contain loops and other artifacts which are not present in the true offset curve. The raw offset line is matched to the buffer ring (which is clean) to extract the offset curve.

Parameters

geom	the linestring to offset
dist	the offset distance
bufParams	the buffer parameters to use
lineList	the vector to populate with the return value

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The documentation for this class was generated from the following file:

• OffsetCurve.h