Contains the parameters which describe how a buffer should be constructed. More...

#include <BufferParameters.h>

Public Types
enum	EndCapStyle { CAP_ROUND = 1 , CAP_FLAT = 2 , CAP_SQUARE = 3 }
	End cap styles. More...

enum	JoinStyle { JOIN_ROUND = 1 , JOIN_MITRE = 2 , JOIN_BEVEL = 3 }
	Join styles. More...

Public Member Functions
	BufferParameters ()
	Creates a default set of parameters.

	BufferParameters (int quadrantSegments)

	BufferParameters (int quadrantSegments, EndCapStyle endCapStyle)
	Creates a set of parameters with the given quadrantSegments and endCapStyle values. More...

	BufferParameters (int quadrantSegments, EndCapStyle endCapStyle, JoinStyle joinStyle, double mitreLimit)
	Creates a set of parameters with the given parameter values. More...

int	getQuadrantSegments () const

void	setQuadrantSegments (int quadSegs)
	Sets the number of line segments used to approximate an angle fillet. More...

EndCapStyle	getEndCapStyle () const

void	setEndCapStyle (EndCapStyle style)

JoinStyle	getJoinStyle () const

void	setJoinStyle (JoinStyle style)
	Sets the join style for outside (reflex) corners between line segments. More...

double	getMitreLimit () const

void	setMitreLimit (double limit)

void	setSingleSided (bool p_isSingleSided)

bool	isSingleSided () const

Static Public Member Functions
static double	bufferDistanceError (int quadSegs)
	Computes the maximum distance error due to a given level of approximation to a true arc. More...

Static Public Attributes
static const int	DEFAULT_QUADRANT_SEGMENTS = 8
	The default number of facets into which to divide a fillet of 90 degrees. More...

static const double	DEFAULT_MITRE_LIMIT

Detailed Description

Contains the parameters which describe how a buffer should be constructed.

Member Enumeration Documentation

◆ EndCapStyle

enum geos::operation::buffer::BufferParameters::EndCapStyle

End cap styles.

Enumerator
CAP_ROUND	Specifies a round line buffer end cap style.
CAP_FLAT	Specifies a flat line buffer end cap style.
CAP_SQUARE	Specifies a square line buffer end cap style.

◆ JoinStyle

enum geos::operation::buffer::BufferParameters::JoinStyle

Join styles.

Enumerator
JOIN_ROUND	Specifies a round join style.
JOIN_MITRE	Specifies a mitre join style.
JOIN_BEVEL	Specifies a bevel join style.

Constructor & Destructor Documentation

◆ BufferParameters() [1/3]

geos::operation::buffer::BufferParameters::BufferParameters ( int quadrantSegments )

Creates a set of parameters with the given quadrantSegments value.

Parameters

quadrantSegments the number of quadrant segments to use

◆ BufferParameters() [2/3]

geos::operation::buffer::BufferParameters::BufferParameters	(	int	quadrantSegments,
		EndCapStyle	endCapStyle
	)

Creates a set of parameters with the given quadrantSegments and endCapStyle values.

Parameters

quadrantSegments	the number of quadrant segments to use
endCapStyle	the end cap style to use

◆ BufferParameters() [3/3]

geos::operation::buffer::BufferParameters::BufferParameters	(	int	quadrantSegments,
		EndCapStyle	endCapStyle,
		JoinStyle	joinStyle,
		double	mitreLimit
	)

Creates a set of parameters with the given parameter values.

Parameters

quadrantSegments	the number of quadrant segments to use
endCapStyle	the end cap style to use
joinStyle	the join style to use
mitreLimit	the mitre limit to use

Member Function Documentation

◆ bufferDistanceError()

static double geos::operation::buffer::BufferParameters::bufferDistanceError ( int quadSegs )

static

Computes the maximum distance error due to a given level of approximation to a true arc.

Parameters

quadSegs the number of segments used to approximate a quarter-circle

Returns: the error of approximation

◆ getEndCapStyle()

EndCapStyle geos::operation::buffer::BufferParameters::getEndCapStyle ( ) const

inline

Gets the end cap style.

Returns: the end cap style

◆ getJoinStyle()

JoinStyle geos::operation::buffer::BufferParameters::getJoinStyle ( ) const

inline

Gets the join style.

Returns: the join style

◆ getMitreLimit()

double geos::operation::buffer::BufferParameters::getMitreLimit ( ) const

inline

Gets the mitre ratio limit.

Returns: the limit value

◆ getQuadrantSegments()

int geos::operation::buffer::BufferParameters::getQuadrantSegments ( ) const

inline

Gets the number of quadrant segments which will be used

Returns: the number of quadrant segments

◆ isSingleSided()

bool geos::operation::buffer::BufferParameters::isSingleSided ( ) const

inline

Tests whether the buffer is to be generated on a single side only.

Returns: true if the generated buffer is to be single-sided

◆ setEndCapStyle()

void geos::operation::buffer::BufferParameters::setEndCapStyle ( EndCapStyle style )

inline

Specifies the end cap style of the generated buffer.

The styles supported are CAP_ROUND, CAP_BUTT, and CAP_SQUARE.

The default is CAP_ROUND.

Parameters

style the end cap style to specify

Referenced by geos::operation::buffer::BufferOp::setEndCapStyle().

◆ setJoinStyle()

void geos::operation::buffer::BufferParameters::setJoinStyle ( JoinStyle style )

inline

Sets the join style for outside (reflex) corners between line segments.

Allowable values are JOIN_ROUND (which is the default), JOIN_MITRE and JOIN_BEVEL.

Parameters

style the code for the join style

◆ setMitreLimit()

void geos::operation::buffer::BufferParameters::setMitreLimit ( double limit )

inline

Sets the limit on the mitre ratio used for very sharp corners.

The mitre ratio is the ratio of the distance from the corner to the end of the mitred offset corner. When two line segments meet at a sharp angle, a miter join will extend far beyond the original geometry. (and in the extreme case will be infinitely far.) To prevent unreasonable geometry, the mitre limit allows controlling the maximum length of the join corner. Corners with a ratio which exceed the limit will be beveled.

Parameters

limit the mitre ratio limit

◆ setQuadrantSegments()

void geos::operation::buffer::BufferParameters::setQuadrantSegments ( int quadSegs )

Sets the number of line segments used to approximate an angle fillet.

If quadSegs >= 1, joins are round, and quadSegs indicates the number of segments to use to approximate a quarter-circle.
If quadSegs = 0, joins are bevelled (flat)
If quadSegs < 0, joins are mitred, and the value of qs indicates the mitre ration limit as
```
   mitreLimit = |quadSegs|
   
```

For round joins, quadSegs determines the maximum error in the approximation to the true buffer curve.

The default value of 8 gives less than 2% max error in the buffer distance.

For a max error of < 1%, use QS = 12. For a max error of < 0.1%, use QS = 18. The error is always less than the buffer distance (in other words, the computed buffer curve is always inside the true curve).

Parameters

quadSegs the number of segments in a fillet for a quadrant

Referenced by geos::operation::buffer::BufferOp::setQuadrantSegments().

◆ setSingleSided()

void geos::operation::buffer::BufferParameters::setSingleSided ( bool p_isSingleSided )

inline

Sets whether the computed buffer should be single-sided. A single-sided buffer is constructed on only one side of each input line.

The side used is determined by the sign of the buffer distance:

a positive distance indicates the left-hand side
a negative distance indicates the right-hand side

The single-sided buffer of point geometries is the same as the regular buffer.

The End Cap Style for single-sided buffers is always ignored, and forced to the equivalent of CAP_FLAT.

Parameters

p_isSingleSided true if a single-sided buffer should be constructed

Referenced by geos::operation::buffer::BufferOp::setSingleSided().

Member Data Documentation

◆ DEFAULT_MITRE_LIMIT

const double geos::operation::buffer::BufferParameters::DEFAULT_MITRE_LIMIT

static

The default mitre limit

Allows fairly pointy mitres.

◆ DEFAULT_QUADRANT_SEGMENTS

const int geos::operation::buffer::BufferParameters::DEFAULT_QUADRANT_SEGMENTS = 8

static

The default number of facets into which to divide a fillet of 90 degrees.

A value of 8 gives less than 2% max error in the buffer distance. For a max error of < 1%, use QS = 12. For a max error of < 0.1%, use QS = 18.

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

BufferParameters.h

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Detailed Description

Member Enumeration Documentation

◆ EndCapStyle

◆ JoinStyle

Constructor & Destructor Documentation

◆ BufferParameters() [1/3]

◆ BufferParameters() [2/3]

◆ BufferParameters() [3/3]

Member Function Documentation

◆ bufferDistanceError()

◆ getEndCapStyle()

◆ getJoinStyle()

◆ getMitreLimit()

◆ getQuadrantSegments()

◆ isSingleSided()

◆ setEndCapStyle()

◆ setJoinStyle()

◆ setMitreLimit()

◆ setQuadrantSegments()

◆ setSingleSided()

Member Data Documentation

◆ DEFAULT_MITRE_LIMIT

◆ DEFAULT_QUADRANT_SEGMENTS