/* * 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.geom.util; import com.vividsolutions.jts.geom.*; import com.vividsolutions.jts.util.*; /** * Creates geometries which are shaped like multi-armed stars * with each arm shaped like a sine wave. * These kinds of geometries are useful as a more complex * geometry for testing algorithms. * * @author Martin Davis * */ public class SineStarFactory extends GeometricShapeFactory { protected int numArms = 8; protected double armLengthRatio = 0.5; /** * Creates a factory which will create sine stars using the default * {@link GeometryFactory}. * * @param geomFact the factory to use */ public SineStarFactory() { super(); } /** * Creates a factory which will create sine stars using the given * {@link GeometryFactory}. * * @param geomFact the factory to use */ public SineStarFactory(GeometryFactory geomFact) { super(geomFact); } /** * Sets the number of arms in the star * * @param numArms the number of arms to generate */ public void setNumArms(int numArms) { this.numArms = numArms; } /** * Sets the ration of the length of each arm to the distance from the tip * of the arm to the centre of the star. * Value should be between 0.0 and 1.0 * * @param armLengthRatio */ public void setArmLengthRatio(double armLengthRatio) { this.armLengthRatio = armLengthRatio; } /** * Generates the geometry for the sine star * * @return the geometry representing the sine star */ public Geometry createSineStar() { Envelope env = dim.getEnvelope(); double radius = env.getWidth() / 2.0; double armRatio = armLengthRatio; if (armRatio < 0.0) armRatio = 0.0; if (armRatio > 1.0) armRatio = 1.0; double armMaxLen = armRatio * radius; double insideRadius = (1 - armRatio) * radius; double centreX = env.getMinX() + radius; double centreY = env.getMinY() + radius; Coordinate[] pts = new Coordinate[nPts + 1]; int iPt = 0; for (int i = 0; i < nPts; i++) { // the fraction of the way thru the current arm - in [0,1] double ptArcFrac = (i / (double) nPts) * numArms; double armAngFrac = ptArcFrac - Math.floor(ptArcFrac); // the angle for the current arm - in [0,2Pi] // (each arm is a complete sine wave cycle) double armAng = 2 * Math.PI * armAngFrac; // the current length of the arm double armLenFrac = (Math.cos(armAng) + 1.0) / 2.0; // the current radius of the curve (core + arm) double curveRadius = insideRadius + armMaxLen * armLenFrac; // the current angle of the curve double ang = i * (2 * Math.PI / nPts); double x = curveRadius * Math.cos(ang) + centreX; double y = curveRadius * Math.sin(ang) + centreY; pts[iPt++] = coord(x, y); } pts[iPt] = new Coordinate(pts[0]); LinearRing ring = geomFact.createLinearRing(pts); Polygon poly = geomFact.createPolygon(ring, null); return poly; } }