org.locationtech.jts.simplify

Class DouglasPeuckerSimplifier

java.lang.Object

org.locationtech.jts.simplify.DouglasPeuckerSimplifier

public class DouglasPeuckerSimplifier
extends Object

Simplifies a Geometry using the Douglas-Peucker 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.

Note that in general D-P 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. To simplify geometry while preserving topology use TopologyPreservingSimplifier. (However, using D-P is significantly faster).

KNOWN BUGS

• In some cases the approach used to clean invalid simplified polygons can distort the output geometry severely.

Version:

1.7

See Also:

TopologyPreservingSimplifier

Constructor Summary

Constructors

Constructor and Description
DouglasPeuckerSimplifier(Geometry inputGeom) Creates a simplifier for a given geometry.

Method Summary

Modifier and Type	Method and Description
Geometry	getResultGeometry() Gets the simplified geometry.
void	setDistanceTolerance(double distanceTolerance) Sets the distance tolerance for the simplification.
void	setEnsureValid(boolean isEnsureValidTopology) Controls whether simplified polygons will be "fixed" to have valid topology.
static Geometry	simplify(Geometry geom, double distanceTolerance) Simplifies a geometry using a given tolerance.

Methods inherited from class java.lang.Object

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

Constructor Detail

DouglasPeuckerSimplifier

public DouglasPeuckerSimplifier(Geometry inputGeom)

Creates a simplifier for a given geometry.

Parameters:

inputGeom - the geometry to simplify

Method Detail

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