org.locationtech.jts.precision

Class GeometryPrecisionReducer

java.lang.Object

org.locationtech.jts.precision.GeometryPrecisionReducer

public class GeometryPrecisionReducer
extends Object

Reduces the precision of a Geometry according to the supplied PrecisionModel, ensuring that the result is valid (unless specified otherwise).

By default the reduced result is topologically valid (i.e. Geometry.isValid() is true). To ensure this a polygonal geometry is reduced in a topologically valid fashion (technically, by using snap-rounding). Note that this may change polygonal geometry structure (e.g. two polygons separated by a distance below the specified precision will be merged into a single polygon).

In general input must be valid geometry, or an IllegalArgumentException will be thrown. However if the invalidity is "mild" or very small then it may be eliminated by precision reduction.

Alternatively, geometry can be reduced pointwise by using setPointwise(boolean). In this case the result geometry topology may be invalid. Linear and point geometry are always reduced pointwise (i.e. without further change to topology or structure), since this does not change validity.

By default the geometry precision model is not changed. This can be overridden by using setChangePrecisionModel(boolean).

Normally collapsed components (e.g. lines collapsing to a point) are not included in the result. This behavior can be changed by using setRemoveCollapsedComponents(boolean).

Version:

1.12

Constructor Summary

Constructors

Constructor and Description
GeometryPrecisionReducer(PrecisionModel pm)

Method Summary

Modifier and Type	Method and Description
Geometry	reduce(Geometry geom) Reduces the precision of a geometry, according to the specified strategy of this reducer.
static Geometry	reduce(Geometry g, PrecisionModel precModel) Convenience method for doing precision reduction on a single geometry, with collapses removed and keeping the geometry precision model the same, and preserving polygonal topology.
static Geometry	reducePointwise(Geometry g, PrecisionModel precModel) Convenience method for doing pointwise precision reduction on a single geometry, with collapses removed and keeping the geometry precision model the same, but NOT preserving valid polygonal topology.
void	setChangePrecisionModel(boolean changePrecisionModel) Sets whether the PrecisionModel of the new reduced Geometry will be changed to be the PrecisionModel supplied to specify the precision reduction.
void	setPointwise(boolean isPointwise) Sets whether the precision reduction will be done in pointwise fashion only.
void	setRemoveCollapsedComponents(boolean removeCollapsed) Sets whether the reduction will result in collapsed components being removed completely, or simply being collapsed to an (invalid) Geometry of the same type.

Methods inherited from class java.lang.Object

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

Constructor Detail

GeometryPrecisionReducer

public GeometryPrecisionReducer(PrecisionModel pm)

Method Detail

reduce

public static Geometry reduce(Geometry g,
                              PrecisionModel precModel)

Convenience method for doing precision reduction on a single geometry, with collapses removed and keeping the geometry precision model the same, and preserving polygonal topology.

Parameters:

g - the geometry to reduce

precModel - the precision model to use

Returns:

the reduced geometry

Throws:

IllegalArgumentException - if the reduction fails due to invalid input geometry is invalid

reducePointwise

public static Geometry reducePointwise(Geometry g,
                                       PrecisionModel precModel)

Convenience method for doing pointwise precision reduction on a single geometry, with collapses removed and keeping the geometry precision model the same, but NOT preserving valid polygonal topology.

Parameters:

g - the geometry to reduce

precModel - the precision model to use

Returns:

the reduced geometry

setRemoveCollapsedComponents

public void setRemoveCollapsedComponents(boolean removeCollapsed)

Sets whether the reduction will result in collapsed components being removed completely, or simply being collapsed to an (invalid) Geometry of the same type. The default is to remove collapsed components.

Parameters:

removeCollapsed - if true collapsed components will be removed

setChangePrecisionModel

public void setChangePrecisionModel(boolean changePrecisionModel)

Sets whether the PrecisionModel of the new reduced Geometry will be changed to be the PrecisionModel supplied to specify the precision reduction.

The default is to not change the precision model

Parameters:

changePrecisionModel - if true the precision model of the created Geometry will be the the precisionModel supplied in the constructor.

setPointwise

public void setPointwise(boolean isPointwise)

Sets whether the precision reduction will be done in pointwise fashion only. Pointwise precision reduction reduces the precision of the individual coordinates only, but does not attempt to recreate valid topology. This is only relevant for geometries containing polygonal components.

Parameters:

isPointwise - if reduction should be done pointwise only

reduce

public Geometry reduce(Geometry geom)

Reduces the precision of a geometry, according to the specified strategy of this reducer.

Parameters:

geom - the geometry to reduce

Returns:

the precision-reduced geometry

Throws:

IllegalArgumentException - if the reduction fails due to invalid input geometry is invalid