org.locationtech.jts.operation.buffer

Class BufferOp

java.lang.Object

org.locationtech.jts.operation.buffer.BufferOp

public class BufferOp
extends Object

Computes the buffer of a geometry, for both positive and negative buffer distances.

In GIS, the positive (or negative) buffer of a geometry is defined as the Minkowski sum (or difference) of the geometry with a circle of radius equal to the absolute value of the buffer distance. In the CAD/CAM world buffers are known as offset curves. In morphological analysis the operation of positive and negative buffering is referred to as erosion and dilation

The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty Polygon.

Since true buffer curves may contain circular arcs, computed buffer polygons are only approximations to the true geometry. The user can control the accuracy of the approximation by specifying the number of linear segments used to approximate arcs. This is specified via BufferParameters.setQuadrantSegments(int) or setQuadrantSegments(int).

The end cap style of a linear buffer may be specified. The following end cap styles are supported:

• BufferParameters.CAP_ROUND - the usual round end caps
• BufferParameters.CAP_FLAT - end caps are truncated flat at the line ends
• BufferParameters.CAP_SQUARE - end caps are squared off at the buffer distance beyond the line ends

The join style of the corners in a buffer may be specified. The following join styles are supported:

• BufferParameters.JOIN_ROUND - the usual round join
• BufferParameters.JOIN_MITRE - corners are "sharp" (up to a distance limit)
• BufferParameters.JOIN_BEVEL - corners are beveled (clipped off).

The buffer algorithm may perform simplification on the input to increase performance. The simplification is performed a way that always increases the buffer area (so that the simplified input covers the original input). The degree of simplification can be specified, with a default used otherwise. Note that if the buffer distance is zero then so is the computed simplify tolerance, no matter what the simplify factor.

Buffer results are always valid geometry. Given this, computing a zero-width buffer of an invalid polygonal geometry is an effective way to "validify" the geometry. Note however that in the case of self-intersecting "bow-tie" geometries, only the largest enclosed area will be retained.

Version:

1.7

Field Summary

Fields

Modifier and Type	Field and Description
static int	CAP_BUTT Deprecated. use BufferParameters
static int	CAP_FLAT Deprecated. use BufferParameters
static int	CAP_ROUND Deprecated. use BufferParameters
static int	CAP_SQUARE Deprecated. use BufferParameters

Constructor Summary

Constructors

Constructor and Description
BufferOp(Geometry g) Initializes a buffer computation for the given geometry
BufferOp(Geometry g, BufferParameters bufParams) Initializes a buffer computation for the given geometry with the given set of parameters

Method Summary

Modifier and Type	Method and Description
static Geometry	bufferOp(Geometry g, double distance) Computes the buffer of a geometry for a given buffer distance.
static Geometry	bufferOp(Geometry g, double distance, BufferParameters params) Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
static Geometry	bufferOp(Geometry g, double distance, int quadrantSegments) Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
static Geometry	bufferOp(Geometry g, double distance, int quadrantSegments, int endCapStyle) Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.
Geometry	getResultGeometry(double distance) Returns the buffer computed for a geometry for a given buffer distance.
void	setEndCapStyle(int endCapStyle) Specifies the end cap style of the generated buffer.
void	setQuadrantSegments(int quadrantSegments) Sets the number of segments used to approximate a angle fillet

Methods inherited from class java.lang.Object

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

Field Detail

CAP_ROUND

public static final int CAP_ROUND

Deprecated. use BufferParameters

Specifies a round line buffer end cap style.

See Also:

Constant Field Values

CAP_BUTT

public static final int CAP_BUTT

Deprecated. use BufferParameters

Specifies a butt (or flat) line buffer end cap style.

See Also:

Constant Field Values

CAP_FLAT

public static final int CAP_FLAT

Deprecated. use BufferParameters

Specifies a butt (or flat) line buffer end cap style.

See Also:

Constant Field Values

CAP_SQUARE

public static final int CAP_SQUARE

Deprecated. use BufferParameters

Specifies a square line buffer end cap style.

See Also:

Constant Field Values

Constructor Detail

BufferOp

public BufferOp(Geometry g)

Initializes a buffer computation for the given geometry

Parameters:

g - the geometry to buffer

BufferOp

public BufferOp(Geometry g,
                BufferParameters bufParams)

Initializes a buffer computation for the given geometry with the given set of parameters

Parameters:

g - the geometry to buffer

bufParams - the buffer parameters to use

Method Detail

bufferOp

public static Geometry bufferOp(Geometry g,
                                double distance)

Computes the buffer of a geometry for a given buffer distance.

Parameters:

g - the geometry to buffer

distance - the buffer distance

Returns:

the buffer of the input geometry

bufferOp

public static Geometry bufferOp(Geometry g,
                                double distance,
                                BufferParameters params)

Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.

Parameters:

g - the geometry to buffer

distance - the buffer distance

params - the buffer parameters to use

Returns:

the buffer of the input geometry

bufferOp

public static Geometry bufferOp(Geometry g,
                                double distance,
                                int quadrantSegments)

Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.

Parameters:

g - the geometry to buffer

distance - the buffer distance

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

Returns:

the buffer of the input geometry

bufferOp

public static Geometry bufferOp(Geometry g,
                                double distance,
                                int quadrantSegments,
                                int endCapStyle)

Computes the buffer for a geometry for a given buffer distance and accuracy of approximation.

Parameters:

g - the geometry to buffer

distance - the buffer distance

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

endCapStyle - the end cap style to use

Returns:

the buffer of the input geometry

setEndCapStyle

public void setEndCapStyle(int endCapStyle)

Specifies the end cap style of the generated buffer. The styles supported are BufferParameters.CAP_ROUND, BufferParameters.CAP_FLAT, and BufferParameters.CAP_SQUARE. The default is CAP_ROUND.

Parameters:

endCapStyle - the end cap style to specify

setQuadrantSegments

public void setQuadrantSegments(int quadrantSegments)

Sets the number of segments used to approximate a angle fillet

Parameters:

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

getResultGeometry

public Geometry getResultGeometry(double distance)

Returns the buffer computed for a geometry for a given buffer distance.

Parameters:

distance - the buffer distance

Returns:

the buffer of the input geometry