Class VWSimplifier

java.lang.Object
org.locationtech.jts.simplify.VWSimplifier

public class VWSimplifier extends Object
Simplifies a Geometry using the Visvalingam-Whyatt area-based algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. All geometry types are handled. Empty and point geometries are returned unchanged. Empty geometry components are deleted.

The simplification tolerance is specified as a distance. This is converted to an area tolerance by squaring it.

Note that in general this algorithm does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross.

Known Bugs

  • Not yet optimized for performance
  • Does not simplify the endpoint of rings

To Do

  • Allow specifying desired number of vertices in the output
Version:
1.7
  • Constructor Details

    • VWSimplifier

      public VWSimplifier(Geometry inputGeom)
      Creates a simplifier for a given geometry.
      Parameters:
      inputGeom - the geometry to simplify
  • Method Details

    • simplify

      public static Geometry simplify(Geometry geom, double distanceTolerance)
      Simplifies a geometry using a given tolerance.
      Parameters:
      geom - geometry to simplify
      distanceTolerance - the tolerance to use
      Returns:
      a simplified version of the geometry
    • setDistanceTolerance

      public void setDistanceTolerance(double distanceTolerance)
      Sets the distance tolerance for the simplification. All vertices in the simplified geometry will be within this distance of the original geometry. The tolerance value must be non-negative.
      Parameters:
      distanceTolerance - the approximation tolerance to use
    • setEnsureValid

      public void setEnsureValid(boolean isEnsureValidTopology)
      Controls whether simplified polygons will be "fixed" to have valid topology. The caller may choose to disable this because:
      • valid topology is not required
      • fixing topology is a relative expensive operation
      • in some pathological cases the topology fixing operation may either fail or run for too long
      The default is to fix polygon topology.
      Parameters:
      isEnsureValidTopology -
    • getResultGeometry

      public Geometry getResultGeometry()
      Gets the simplified geometry.
      Returns:
      the simplified geometry