com.revolsys.jts.operation.overlay

Class OverlayOp

java.lang.Object

com.revolsys.jts.operation.GeometryGraphOperation

com.revolsys.jts.operation.overlay.OverlayOp

public class OverlayOp
extends GeometryGraphOperation

Computes the geometric overlay of two Geometrys. The overlay can be used to determine any boolean combination of the geometries.

Version:

1.7

Field Summary

Fields

Modifier and Type	Field and Description
static int	DIFFERENCE The code for the Difference overlay operation.
static int	INTERSECTION The code for the Intersection overlay operation.
static int	SYMDIFFERENCE The code for the Symmetric Difference overlay operation.
static int	UNION The code for the Union overlay operation.

Fields inherited from class com.revolsys.jts.operation.GeometryGraphOperation

arg, li

Constructor Summary

Constructors

Constructor and Description
OverlayOp(Geometry g0, Geometry g1) Constructs an instance to compute a single overlay operation for the given geometries.

Method Summary

Methods

Modifier and Type	Method and Description
static Geometry	createEmptyResult(int overlayOpCode, Geometry a, Geometry b, GeometryFactory geomFact) Creates an empty result geometry of the appropriate dimension, based on the given overlay operation and the dimensions of the inputs.
PlanarGraph	getGraph() Gets the graph constructed to compute the overlay.
Geometry	getResultGeometry(int overlayOpCode) Gets the result of the overlay for a given overlay operation.
protected void	insertUniqueEdge(Edge e) Insert an edge from one of the noded input graphs.
boolean	isCoveredByA(Point coord) Tests if an L edge should be included in the result or not.
boolean	isCoveredByLA(Point coord) Tests if a point node should be included in the result or not.
static boolean	isResultOfOp(Label label, int opCode) Tests whether a point with a given topological Label relative to two geometries is contained in the result of overlaying the geometries using a given overlay operation.
static boolean	isResultOfOp(Location loc0, Location loc1, int overlayOpCode) Tests whether a point with given Locations relative to two geometries is contained in the result of overlaying the geometries using a given overlay operation.
static Geometry	overlayOp(Geometry geom0, Geometry geom1, int opCode) Computes an overlay operation for the given geometry arguments.

Methods inherited from class com.revolsys.jts.operation.GeometryGraphOperation

getArgGeometry, setComputationPrecision

Methods inherited from class java.lang.Object

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

Field Detail

INTERSECTION

public static final int INTERSECTION

The code for the Intersection overlay operation.

See Also:

Constant Field Values

UNION

public static final int UNION

The code for the Union overlay operation.

See Also:

Constant Field Values

DIFFERENCE

public static final int DIFFERENCE

The code for the Difference overlay operation.

See Also:

Constant Field Values

SYMDIFFERENCE

public static final int SYMDIFFERENCE

The code for the Symmetric Difference overlay operation.

See Also:

Constant Field Values

Constructor Detail

OverlayOp

public OverlayOp(Geometry g0,
         Geometry g1)

Constructs an instance to compute a single overlay operation for the given geometries.

Parameters:

g0 - the first geometry argument

g1 - the second geometry argument

Method Detail

createEmptyResult

public static Geometry createEmptyResult(int overlayOpCode,
                         Geometry a,
                         Geometry b,
                         GeometryFactory geomFact)

Creates an empty result geometry of the appropriate dimension, based on the given overlay operation and the dimensions of the inputs. The created geometry is always an atomic geometry, not a collection.

The empty result is constructed using the following rules:

• INTERSECTION - result has the dimension of the lowest input dimension
• UNION - result has the dimension of the highest input dimension
• DIFFERENCE - result has the dimension of the left-hand input
• SYMDIFFERENCE - result has the dimension of the highest input dimension (since the symmetric Difference is the union of the differences).

Parameters:

overlayOpCode - the code for the overlay operation being performed

a - an input geometry

b - an input geometry

geomFact - the geometry factory being used for the operation

Returns:

an empty atomic geometry of the appropriate dimension

isResultOfOp

public static boolean isResultOfOp(Label label,
                   int opCode)

Tests whether a point with a given topological Label relative to two geometries is contained in the result of overlaying the geometries using a given overlay operation.

The method handles arguments of Location.NONE correctly

Parameters:

label - the topological label of the point

opCode - the code for the overlay operation to test

Returns:

true if the label locations correspond to the overlayOpCode

isResultOfOp

public static boolean isResultOfOp(Location loc0,
                   Location loc1,
                   int overlayOpCode)

Tests whether a point with given Locations relative to two geometries is contained in the result of overlaying the geometries using a given overlay operation.

The method handles arguments of Location.NONE correctly

Parameters:

loc0 - the code for the location in the first geometry

loc1 - the code for the location in the second geometry

overlayOpCode - the code for the overlay operation to test

Returns:

true if the locations correspond to the overlayOpCode

overlayOp

public static Geometry overlayOp(Geometry geom0,
                 Geometry geom1,
                 int opCode)

Computes an overlay operation for the given geometry arguments.

Parameters:

geom0 - the first geometry argument

geom1 - the second geometry argument

opCode - the code for the desired overlay operation

Returns:

the result of the overlay operation

Throws:

TopologyException - if a robustness problem is encountered

getGraph

public PlanarGraph getGraph()

Gets the graph constructed to compute the overlay.

Returns:

the overlay graph

getResultGeometry

public Geometry getResultGeometry(int overlayOpCode)

Gets the result of the overlay for a given overlay operation.

Note: this method can be called once only.

Parameters:

overlayOpCode - the overlay operation to perform

Returns:

the compute result geometry

Throws:

TopologyException - if a robustness problem is encountered

insertUniqueEdge

protected void insertUniqueEdge(Edge e)

Insert an edge from one of the noded input graphs. Checks edges that are inserted to see if an identical edge already exists. If so, the edge is not inserted, but its label is merged with the existing edge.

isCoveredByA

public boolean isCoveredByA(Point coord)

Tests if an L edge should be included in the result or not.

Parameters:

coord - the point coordinate

Returns:

true if the coordinate point is covered by a result Area geometry

isCoveredByLA

public boolean isCoveredByLA(Point coord)

Tests if a point node should be included in the result or not.

Parameters:

coord - the point coordinate

Returns:

true if the coordinate point is covered by a result Line or Area geometry