public class GeometryTransformer extends Object
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)transformMultiPolygon
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)transform
method itself will always
return a non-null Geometry object (but this may be empty).
GeometryEditor
Modifier and Type | Field and Description |
---|---|
protected GeometryFactory |
factory |
Constructor and Description |
---|
GeometryTransformer() |
protected GeometryFactory factory
public Geometry getInputGeometry()
protected final CoordinateSequence createCoordinateSequence(Coordinate[] coords)
CoordinateSequence
coords
- the coordinate array to copyprotected final CoordinateSequence copy(CoordinateSequence seq)
CoordinateSequence
sseq
- the sequence to copyprotected CoordinateSequence transformCoordinates(CoordinateSequence coords, Geometry parent)
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.coords
- the coordinates to transformparent
- the parent geometryprotected Geometry transformMultiPoint(MultiPoint geom, Geometry parent)
protected Geometry transformLinearRing(LinearRing geom, Geometry parent)
geom
- the ring to simplifyparent
- the parent geometryprotected Geometry transformLineString(LineString geom, Geometry parent)
LineString
geometry.geom
- parent
- protected Geometry transformMultiLineString(MultiLineString geom, Geometry parent)
protected Geometry transformMultiPolygon(MultiPolygon geom, Geometry parent)
protected Geometry transformGeometryCollection(GeometryCollection geom, Geometry parent)
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