com.vividsolutions.jts.operation.buffer
Class BufferParameters

java.lang.Object
  com.vividsolutions.jts.operation.buffer.BufferParameters

public class BufferParameters
extends java.lang.Object

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

Author:

Martin Davis

Field Summary

static int	CAP_FLAT Specifies a flat line buffer end cap style.
static int	CAP_ROUND Specifies a round line buffer end cap style.
static int	CAP_SQUARE Specifies a square line buffer end cap style.
static double	DEFAULT_MITRE_LIMIT The default mitre limit Allows fairly pointy mitres.
static int	DEFAULT_QUADRANT_SEGMENTS The default number of facets into which to divide a fillet of 90 degrees.
static int	JOIN_BEVEL Specifies a bevel join style.
static int	JOIN_MITRE Specifies a mitre join style.
static int	JOIN_ROUND Specifies a round join style.

Constructor Summary

BufferParameters()
Creates a default set of parameters

BufferParameters(int quadrantSegments)
Creates a set of parameters with the given quadrantSegments value.

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

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

Method Summary

static double	bufferDistanceError(int quadSegs) Computes the maximum distance error due to a given level of approximation to a true arc.
int	getEndCapStyle() Gets the end cap style.
int	getJoinStyle() Gets the join style
double	getMitreLimit() Gets the mitre ratio limit.
int	getQuadrantSegments() Gets the number of quadrant segments which will be used
boolean	isSingleSided() Tests whether the buffer is to be generated on a single side only.
void	setEndCapStyle(int endCapStyle) Specifies the end cap style of the generated buffer.
void	setJoinStyle(int joinStyle) Sets the join style for outside (reflex) corners between line segments.
void	setMitreLimit(double mitreLimit) Sets the limit on the mitre ratio used for very sharp corners.
void	setQuadrantSegments(int quadSegs) Sets the number of line segments used to approximate an angle fillet.
void	setSingleSided(boolean isSingleSided) Sets whether the computed buffer should be single-sided.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CAP_ROUND

public static final int CAP_ROUND

Specifies a round line buffer end cap style.

See Also:

Constant Field Values

CAP_FLAT

public static final int CAP_FLAT

Specifies a flat line buffer end cap style.

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Constant Field Values

CAP_SQUARE

public static final int CAP_SQUARE

Specifies a square line buffer end cap style.

See Also:

Constant Field Values

JOIN_ROUND

public static final int JOIN_ROUND

Specifies a round join style.

See Also:

Constant Field Values

JOIN_MITRE

public static final int JOIN_MITRE

Specifies a mitre join style.

See Also:

Constant Field Values

JOIN_BEVEL

public static final int JOIN_BEVEL

Specifies a bevel join style.

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Constant Field Values

DEFAULT_QUADRANT_SEGMENTS

public static final int DEFAULT_QUADRANT_SEGMENTS

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.

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Constant Field Values

DEFAULT_MITRE_LIMIT

public static final double DEFAULT_MITRE_LIMIT

The default mitre limit Allows fairly pointy mitres.

See Also:

Constant Field Values

Constructor Detail

BufferParameters

public BufferParameters()

Creates a default set of parameters

BufferParameters

public BufferParameters(int quadrantSegments)

Creates a set of parameters with the given quadrantSegments value.

Parameters:

quadrantSegments - the number of quadrant segments to use

BufferParameters

public BufferParameters(int quadrantSegments,
                        int 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

public BufferParameters(int quadrantSegments,
                        int endCapStyle,
                        int 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

Method Detail

getQuadrantSegments

public int getQuadrantSegments()

Gets the number of quadrant segments which will be used

Returns:

the number of quadrant segments

setQuadrantSegments

public void 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:

quadrantSegments - the number of segments in a fillet for a quadrant

bufferDistanceError

public static double bufferDistanceError(int quadSegs)

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

public int getEndCapStyle()

Gets the end cap style.

Returns:

the end cap style

setEndCapStyle

public void setEndCapStyle(int endCapStyle)

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:

endCapStyle - the end cap style to specify

getJoinStyle

public int getJoinStyle()

Gets the join style

Returns:

the join style code

setJoinStyle

public void setJoinStyle(int joinStyle)

Sets the join style for outside (reflex) corners between line segments. Allowable values are JOIN_ROUND (which is the default), JOIN_MITRE and {link JOIN_BEVEL}.

Parameters:

joinStyle - the code for the join style

getMitreLimit

public double getMitreLimit()

Gets the mitre ratio limit.

Returns:

the limit value

setMitreLimit

public void setMitreLimit(double mitreLimit)

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:

mitreLimit - the mitre ratio limit

setSingleSided

public void setSingleSided(boolean isSingleSided)

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:

isSingleSided - true if a single-sided buffer should be constructed

isSingleSided

public boolean isSingleSided()

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

Returns:

true if the generated buffer is to be single-sided