org.locationtech.jts.geom.util

Class GeometryTransformer

java.lang.Object

org.locationtech.jts.geom.util.GeometryTransformer

public class GeometryTransformer
extends Object

A framework for processes which transform an input Geometry into an output Geometry, possibly changing its structure and type(s). This class is a framework for implementing subclasses which perform transformations on various different Geometry subclasses. It provides an easy way of applying specific transformations to given geometry types, while allowing unhandled types to be simply copied. Also, the framework ensures that if subcomponents change type the parent geometries types change appropriately to maintain valid structure. Subclasses will override whichever transformX methods they need to to handle particular Geometry types.

A typically usage would be a transformation class that transforms Polygons into Polygons, LineStrings or Points, depending on the geometry of the input (For instance, a simplification operation). This class would likely need to override the transformMultiPolygon(MultiPolygon, Geometry) method to ensure that if input Polygons change type the result is a GeometryCollection, not a MultiPolygon.

The default behaviour of this class is simply to recursively transform each Geometry component into an identical object by deep copying down to the level of, but not including, coordinates.

All transformX methods may return null, to avoid creating empty or invalid geometry objects. This will be handled correctly by the transformer. transformXXX methods should always return valid geometry - if they cannot do this they should return null (for instance, it may not be possible for a transformLineString implementation to return at least two points - in this case, it should return null). The transform(Geometry) method itself will always return a non-null Geometry object (but this may be empty).

Version:

1.7

See Also:

GeometryEditor

Field Summary

Fields

Modifier and Type	Field and Description
protected GeometryFactory	factory

Constructor Summary

Constructors

Constructor and Description
GeometryTransformer()

Method Summary

Modifier and Type	Method and Description
protected CoordinateSequence	copy(CoordinateSequence seq) Convenience method which provides a standard way of copying CoordinateSequences
protected CoordinateSequence	createCoordinateSequence(Coordinate[] coords) Convenience method which provides standard way of creating a CoordinateSequence
Geometry	getInputGeometry() Utility function to make input geometry available
Geometry	transform(Geometry inputGeom)
protected CoordinateSequence	transformCoordinates(CoordinateSequence coords, Geometry parent) Transforms a CoordinateSequence.
protected Geometry	transformGeometryCollection(GeometryCollection geom, Geometry parent)
protected Geometry	transformLinearRing(LinearRing geom, Geometry parent) Transforms a LinearRing.
protected Geometry	transformLineString(LineString geom, Geometry parent) Transforms a LineString geometry.
protected Geometry	transformMultiLineString(MultiLineString geom, Geometry parent)
protected Geometry	transformMultiPoint(MultiPoint geom, Geometry parent)
protected Geometry	transformMultiPolygon(MultiPolygon geom, Geometry parent)
protected Geometry	transformPoint(Point geom, Geometry parent)
protected Geometry	transformPolygon(Polygon geom, Geometry parent)

Methods inherited from class java.lang.Object

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

Field Detail

factory

protected GeometryFactory factory

Constructor Detail

GeometryTransformer

public GeometryTransformer()

Method Detail

getInputGeometry

public Geometry getInputGeometry()

Utility function to make input geometry available

Returns:

the input geometry

transform

public final Geometry transform(Geometry inputGeom)

createCoordinateSequence

protected final CoordinateSequence createCoordinateSequence(Coordinate[] coords)

Convenience method which provides standard way of creating a CoordinateSequence

Parameters:

coords - the coordinate array to copy

Returns:

a coordinate sequence for the array

copy

protected final CoordinateSequence copy(CoordinateSequence seq)

Convenience method which provides a standard way of copying CoordinateSequences

Parameters:

seq - the sequence to copy

Returns:

a deep copy of the sequence

transformCoordinates

protected CoordinateSequence transformCoordinates(CoordinateSequence coords,
                                                  Geometry parent)

Transforms a CoordinateSequence. This method should always return a valid coordinate list for the desired result type. (E.g. a coordinate list for a LineString must have 0 or at least 2 points). If this is not possible, return an empty sequence - this will be pruned out.

Parameters:

coords - the coordinates to transform

parent - the parent geometry

Returns:

the transformed coordinates

transformPoint

protected Geometry transformPoint(Point geom,
                                  Geometry parent)

transformMultiPoint

protected Geometry transformMultiPoint(MultiPoint geom,
                                       Geometry parent)

transformLinearRing

protected Geometry transformLinearRing(LinearRing geom,
                                       Geometry parent)

Transforms a LinearRing. The transformation of a LinearRing may result in a coordinate sequence which does not form a structurally valid ring (i.e. a degenerate ring of 3 or fewer points). In this case a LineString is returned. Subclasses may wish to override this method and check for this situation (e.g. a subclass may choose to eliminate degenerate linear rings)

Parameters:

geom - the ring to simplify

parent - the parent geometry

Returns:

a LinearRing if the transformation resulted in a structurally valid ring

transformLineString

protected Geometry transformLineString(LineString geom,
                                       Geometry parent)

Transforms a LineString geometry.

Parameters:

geom -

parent -

Returns:

transformMultiLineString

protected Geometry transformMultiLineString(MultiLineString geom,
                                            Geometry parent)

transformPolygon

protected Geometry transformPolygon(Polygon geom,
                                    Geometry parent)

transformMultiPolygon

protected Geometry transformMultiPolygon(MultiPolygon geom,
                                         Geometry parent)

transformGeometryCollection

protected Geometry transformGeometryCollection(GeometryCollection geom,
                                               Geometry parent)