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:

  • Field Details

  • Constructor Details

    • GeometryTransformer

      public GeometryTransformer()

  • Method Details

    • 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)