org.geotools.geometry.jts

Class GeometryClipper

Object

GeometryClipper

public class GeometryClipper
extends Object

A stateful geometry clipper, can clip linestring on a specified rectangle. Trivial benchmarks report a speedup factor between 20 and 60 compared to JTS generic intersection algorithm. The class is not thread safe.

Author:

Andrea Aime - OpenGeo

Constructor Summary

Constructors

Constructor and Description
GeometryClipper(Envelope bounds)

Method Summary

Modifier and Type	Method and Description
Geometry	clip(Geometry g, boolean ensureValid) Clips the geometry on the specified bounds.
Geometry	clipSafe(Geometry g, boolean ensureValid, double scale) This will try to handle failures when clipping - i.e. because of invalid input geometries (often caused by simplification).
Envelope	getBounds()

Methods inherited from class Object

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

Constructor Detail

GeometryClipper

public GeometryClipper(Envelope bounds)

Method Detail

getBounds

public Envelope getBounds()

clipSafe

public Geometry clipSafe(Geometry g,
                         boolean ensureValid,
                         double scale)

This will try to handle failures when clipping - i.e. because of invalid input geometries (often caused by simplification).

This attempts to do a normal clip(). If it fails, it will try to do more to ensure the clip works properly.

1. if its a polygon/multipolygon it will try to make the polygon valid and re-try the clip
2. it will attempt to put the geometry on a precision grid (this will move the points around) and re-try the clip
3. will attempt to clip with ensureValid = false (ie geotools simple clipping)

See clip

Parameters:

scale - Scale used to snap geometry to precision model, 0 to disable

Returns:

a clipped geometry, which may be empty, or null

clip

public Geometry clip(Geometry g,
                     boolean ensureValid)

Clips the geometry on the specified bounds.

Parameters:

g - The geometry to be clipped

ensureValid - If false there is no guarantee the polygons returned will be valid according to JTS rules (but should still be good enough to be used for pure rendering)