package com.vividsolutions.jts.shape.random;
import com.vividsolutions.jts.algorithm.locate.IndexedPointInAreaLocator;
import com.vividsolutions.jts.algorithm.locate.PointOnGeometryLocator;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.shape.GeometricShapeBuilder;
/**
* Creates random point sets contained in a
* region defined by either a rectangular or a polygonal extent.
*
* @author mbdavis
*
*/
public class RandomPointsBuilder
extends GeometricShapeBuilder
{
protected Geometry maskPoly = null;
private PointOnGeometryLocator extentLocator;
/**
* Create a shape factory which will create shapes using the default
* {@link GeometryFactory}.
*/
public RandomPointsBuilder()
{
super(new GeometryFactory());
}
/**
* Create a shape factory which will create shapes using the given
* {@link GeometryFactory}.
*
* @param geomFact the factory to use
*/
public RandomPointsBuilder(GeometryFactory geomFact)
{
super(geomFact);
}
/**
* Sets a polygonal mask.
*
* @param mask
* @ throws IllegalArgumentException if the mask is not polygonal
*/
public void setExtent(Geometry mask)
{
if (! (mask instanceof Polygonal))
throw new IllegalArgumentException("Only polygonal extents are supported");
this.maskPoly = mask;
setExtent(mask.getEnvelopeInternal());
extentLocator = new IndexedPointInAreaLocator(mask);
}
public Geometry getGeometry()
{
Coordinate[] pts = new Coordinate[numPts];
int i = 0;
while (i < numPts) {
Coordinate p = createRandomCoord(getExtent());
if (extentLocator != null && ! isInExtent(p))
continue;
pts[i++] = p;
}
return geomFactory.createMultiPoint(pts);
}
protected boolean isInExtent(Coordinate p)
{
if (extentLocator != null)
return extentLocator.locate(p) != Location.EXTERIOR;
return getExtent().contains(p);
}
protected Coordinate createCoord(double x, double y)
{
Coordinate pt = new Coordinate(x, y);
geomFactory.getPrecisionModel().makePrecise(pt);
return pt;
}
protected Coordinate createRandomCoord(Envelope env)
{
double x = env.getMinX() + env.getWidth() * Math.random();
double y = env.getMinY() + env.getHeight() * Math.random();
return createCoord(x, y);
}
}