com.vividsolutions.jts.shape.random.RandomPointsInGridBuilder Maven / Gradle / Ivy
/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.vividsolutions.jts.shape.random;
import java.util.ArrayList;
import java.util.List;
import com.vividsolutions.jts.algorithm.locate.IndexedPointInAreaLocator;
import com.vividsolutions.jts.algorithm.locate.PointOnGeometryLocator;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.math.MathUtil;
import com.vividsolutions.jts.shape.GeometricShapeBuilder;
/**
* Creates random point sets
* where the points are constrained to lie in the cells of a grid.
*
* @author mbdavis
*
*/
public class RandomPointsInGridBuilder
extends GeometricShapeBuilder
{
private boolean isConstrainedToCircle = false;
private double gutterFraction = 0;
/**
* Create a builder which will create shapes using the default
* {@link GeometryFactory}.
*/
public RandomPointsInGridBuilder()
{
super(new GeometryFactory());
}
/**
* Create a builder which will create shapes using the given
* {@link GeometryFactory}.
*
* @param geomFact the factory to use
*/
public RandomPointsInGridBuilder(GeometryFactory geomFact)
{
super(geomFact);
}
/**
* Sets whether generated points are constrained to lie
* within a circle contained within each grid cell.
* This provides greater separation between points
* in adjacent cells.
*
* The default is to not be constrained to a circle.
* @param isConstrainedToCircle
*/
public void setConstrainedToCircle(boolean isConstrainedToCircle)
{
this.isConstrainedToCircle = isConstrainedToCircle;
}
/**
* Sets the fraction of the grid cell side which will be treated as
* a gutter, in which no points will be created.
* The provided value is clamped to the range [0.0, 1.0].
*
* @param gutterFraction
*/
public void setGutterFraction(double gutterFraction)
{
this.gutterFraction = gutterFraction;
}
/**
* Gets the {@link MultiPoint} containing the generated point
*
* @return a MultiPoint
*/
public Geometry getGeometry()
{
int nCells = (int) Math.sqrt(numPts);
// ensure that at least numPts points are generated
if (nCells * nCells < numPts)
nCells += 1;
double gridDX = getExtent().getWidth() / nCells;
double gridDY = getExtent().getHeight() / nCells;
double gutterFrac = MathUtil.clamp(gutterFraction, 0.0, 1.0);
double gutterOffsetX = gridDX * gutterFrac/2;
double gutterOffsetY = gridDY * gutterFrac/2;
double cellFrac = 1.0 - gutterFrac;
double cellDX = cellFrac * gridDX;
double cellDY = cellFrac * gridDY;
Coordinate[] pts = new Coordinate[nCells * nCells];
int index = 0;
for (int i = 0; i < nCells; i++) {
for (int j = 0; j < nCells; j++) {
double orgX = getExtent().getMinX() + i * gridDX + gutterOffsetX;
double orgY = getExtent().getMinY() + j * gridDY + gutterOffsetY;
pts[index++] = randomPointInCell(orgX, orgY, cellDX, cellDY);
}
}
return geomFactory.createMultiPoint(pts);
}
private Coordinate randomPointInCell(double orgX, double orgY, double xLen, double yLen)
{
if (isConstrainedToCircle) {
return randomPointInCircle(
orgX,
orgY,
xLen, yLen);
}
return randomPointInGridCell(orgX, orgY, xLen, yLen);
}
private Coordinate randomPointInGridCell(double orgX, double orgY, double xLen, double yLen)
{
double x = orgX + xLen * Math.random();
double y = orgY + yLen * Math.random();
return createCoord(x, y);
}
private static Coordinate randomPointInCircle(double orgX, double orgY, double width, double height)
{
double centreX = orgX + width/2;
double centreY = orgY + height/2;
double rndAng = 2 * Math.PI * Math.random();
double rndRadius = Math.random();
// use square root of radius, since area is proportional to square of radius
double rndRadius2 = Math.sqrt(rndRadius);
double rndX = width/2 * rndRadius2 * Math.cos(rndAng);
double rndY = height/2 * rndRadius2 * Math.sin(rndAng);
double x0 = centreX + rndX;
double y0 = centreY + rndY;
return new Coordinate(x0, y0);
}
}