com.vividsolutions.jts.simplify
Class TopologyPreservingSimplifier

java.lang.Object
  com.vividsolutions.jts.simplify.TopologyPreservingSimplifier

public class TopologyPreservingSimplifier
extends java.lang.Object

Simplifies a geometry, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm.

In particular, if the input is an areal geometry ( Polygon or MultiPolygon ):

• The result has the same number of shells and holes (rings) as the input, in the same order
• The result rings touch at no more than the number of touching point in the input (although they may touch at fewer points). (The key implication of this constraint is that the output will be topologically valid if the input was.)

KNOWN BUGS

• If a small hole is very near an edge, it is possible for the edge to be moved by a relatively large tolerance value and end up with the hole outside the result shell. Similarly, it is possible for a small polygon component to end up inside a nearby larger polygon. A workaround is to test for this situation in post-processing and remove any invalid holes or polygons.

Author:

Martin Davis

See Also:

DouglasPeuckerSimplifier

Constructor Summary

TopologyPreservingSimplifier(Geometry inputGeom)

Method Summary

Geometry	getResultGeometry()
void	setDistanceTolerance(double distanceTolerance) Sets the distance tolerance for the simplification.
static Geometry	simplify(Geometry geom, double distanceTolerance)

Methods inherited from class java.lang.Object

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

Constructor Detail

TopologyPreservingSimplifier

public TopologyPreservingSimplifier(Geometry inputGeom)

Method Detail

simplify

public static Geometry simplify(Geometry geom,
                                double distanceTolerance)

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. A tolerance value of zero is effectively a no-op.

Parameters:

distanceTolerance - the approximation tolerance to use

getResultGeometry

public Geometry getResultGeometry()