org.locationtech.jts.operation.polygonize

Class Polygonizer

java.lang.Object

org.locationtech.jts.operation.polygonize.Polygonizer

public class Polygonizer
extends Object

Polygonizes a set of Geometrys which contain linework that represents the edges of a planar graph. All types of Geometry are accepted as input; the constituent linework is extracted as the edges to be polygonized. The processed edges must be correctly noded; that is, they must only meet at their endpoints. Polygonization will accept incorrectly noded input but will not form polygons from non-noded edges, and reports them as errors.

The Polygonizer reports the follow kinds of errors:

• Dangles - edges which have one or both ends which are not incident on another edge endpoint
• Cut Edges - edges which are connected at both ends but which do not form part of polygon
• Invalid Ring Lines - edges which form rings which are invalid (e.g. the component lines contain a self-intersection)

The Polygonizer(boolean) constructor allows extracting only polygons which form a valid polygonal result. The set of extracted polygons is guaranteed to be edge-disjoint. This is useful where it is known that the input lines form a valid polygonal geometry (which may include holes or nested polygons).

Version:

1.7

Constructor Summary

Constructors

Constructor and Description
Polygonizer() Creates a polygonizer that extracts all polygons.
Polygonizer(boolean extractOnlyPolygonal) Creates a polygonizer, specifying whether a valid polygonal geometry must be created.

Method Summary

Modifier and Type	Method and Description
void	add(Collection geomList) Adds a collection of geometries to the edges to be polygonized.
void	add(Geometry g) Add a Geometry to the edges to be polygonized.
Collection	getCutEdges() Gets the list of cut edges found during polygonization.
Collection	getDangles() Gets the list of dangling lines found during polygonization.
Geometry	getGeometry() Gets a geometry representing the polygons formed by the polygonization.
Collection	getInvalidRingLines() Gets the list of lines forming invalid rings found during polygonization.
Collection	getPolygons() Gets the list of polygons formed by the polygonization.
void	setCheckRingsValid(boolean isCheckingRingsValid) Allows disabling the valid ring checking, to optimize situations where invalid rings are not expected.

Methods inherited from class java.lang.Object

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

Constructor Detail

Polygonizer

public Polygonizer()

Creates a polygonizer that extracts all polygons.

Polygonizer

public Polygonizer(boolean extractOnlyPolygonal)

Creates a polygonizer, specifying whether a valid polygonal geometry must be created. If the argument is true then areas may be discarded in order to ensure that the extracted geometry is a valid polygonal geometry.

Parameters:

extractOnlyPolygonal - true if a valid polygonal geometry should be extracted

Method Detail

add

public void add(Collection geomList)

Adds a collection of geometries to the edges to be polygonized. May be called multiple times. Any dimension of Geometry may be added; the constituent linework will be extracted and used.

Parameters:

geomList - a list of Geometrys with linework to be polygonized

add

public void add(Geometry g)

Add a Geometry to the edges to be polygonized. May be called multiple times. Any dimension of Geometry may be added; the constituent linework will be extracted and used

Parameters:

g - a Geometry with linework to be polygonized

setCheckRingsValid

public void setCheckRingsValid(boolean isCheckingRingsValid)

Allows disabling the valid ring checking, to optimize situations where invalid rings are not expected.

The default is true.

Parameters:

isCheckingRingsValid - true if generated rings should be checked for validity

getPolygons

public Collection getPolygons()

Gets the list of polygons formed by the polygonization.

Returns:

a collection of Polygons

getGeometry

public Geometry getGeometry()

Gets a geometry representing the polygons formed by the polygonization. If a valid polygonal geometry was extracted the result is a Polygonal geometry.

Returns:

a geometry containing the polygons

getDangles

public Collection getDangles()

Gets the list of dangling lines found during polygonization.

Returns:

a collection of the input LineStrings which are dangles

getCutEdges

public Collection getCutEdges()

Gets the list of cut edges found during polygonization.

Returns:

a collection of the input LineStrings which are cut edges

getInvalidRingLines

public Collection getInvalidRingLines()

Gets the list of lines forming invalid rings found during polygonization.

Returns:

a collection of the input LineStrings which form invalid rings