package com.vividsolutions.jts.shape.fractal;
import java.util.*;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.shape.*;
public class SierpinskiCarpetBuilder
extends GeometricShapeBuilder
{
private CoordinateList coordList = new CoordinateList();
public SierpinskiCarpetBuilder(GeometryFactory geomFactory)
{
super(geomFactory);
}
public static int recursionLevelForSize(int numPts)
{
double pow4 = numPts / 3;
double exp = Math.log(pow4)/Math.log(4);
return (int) exp;
}
public Geometry getGeometry()
{
int level = recursionLevelForSize(numPts);
LineSegment baseLine = getSquareBaseLine();
Coordinate origin = baseLine.getCoordinate(0);
LinearRing[] holes = getHoles(level, origin.x, origin.y, getDiameter());
LinearRing shell = (LinearRing) ((Polygon) geomFactory.toGeometry(getSquareExtent())).getExteriorRing();
return geomFactory.createPolygon(
shell, holes);
}
private LinearRing[] getHoles(int n, double originX, double originY, double width)
{
List holeList = new ArrayList();
addHoles(n, originX, originY, width, holeList );
return GeometryFactory.toLinearRingArray(holeList);
}
private void addHoles(int n, double originX, double originY, double width, List holeList)
{
if (n < 0) return;
int n2 = n - 1;
double widthThird = width / 3.0;
double widthTwoThirds = width * 2.0 / 3.0;
double widthNinth = width / 9.0;
addHoles(n2, originX, originY, widthThird, holeList);
addHoles(n2, originX + widthThird, originY, widthThird, holeList);
addHoles(n2, originX + 2 * widthThird, originY, widthThird, holeList);
addHoles(n2, originX, originY + widthThird, widthThird, holeList);
addHoles(n2, originX + 2 * widthThird, originY + widthThird, widthThird, holeList);
addHoles(n2, originX, originY + 2 * widthThird, widthThird, holeList);
addHoles(n2, originX + widthThird, originY + 2 * widthThird, widthThird, holeList);
addHoles(n2, originX + 2 * widthThird, originY + 2 * widthThird, widthThird, holeList);
// add the centre hole
holeList.add(createSquareHole(originX + widthThird, originY + widthThird, widthThird));
}
private LinearRing createSquareHole(double x, double y, double width)
{
Coordinate[] pts = new Coordinate[]{
new Coordinate(x, y),
new Coordinate(x + width, y),
new Coordinate(x + width, y + width),
new Coordinate(x, y + width),
new Coordinate(x, y)
} ;
return geomFactory.createLinearRing(pts);
}
}