PolygonGenerator.java
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.generator;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.Polygon;
import org.locationtech.jts.operation.valid.IsValidOp;
/**
*
* This class is used to create a polygon within the specified bounding box.
*
* Successive calls to create may or may not return the same geometry topology.
*
* @author David Zwiers, Vivid Solutions.
*/
public class PolygonGenerator extends GeometryGenerator {
protected int numberPoints = 4;
protected int numberHoles = 0;
protected int generationAlgorithm = 0;
/**
* Creates rectangular polygons
*/
public static final int BOX = 0;
/**
* Creates polygons whose points will not be rectangular when there are more than 4 points
*/
public static final int ARC = 1;
private static final int RUNS = 5;
/**
* As the user increases the number of points, the probability of creating a random valid polygon decreases.
* Please take not of this when selecting the generation style, and the number of points.
*
* May return null if a geometry could not be created.
*
* @see #getNumberPoints()
* @see #setNumberPoints(int)
* @see #getGenerationAlgorithm()
* @see #setGenerationAlgorithm(int)
*
* @see #BOX
* @see #ARC
*
* @see org.locationtech.jts.generator.GeometryGenerator#create()
*
* @throws IllegalStateException When the alg is not valid or the number of points is invalid
* @throws NullPointerException when either the Geometry Factory, or the Bounding Box are undefined.
*/
public Geometry create() {
if(geometryFactory == null){
throw new NullPointerException("GeometryFactory is not declared");
}
if(boundingBox == null || boundingBox.isNull()){
throw new NullPointerException("Bounding Box is not declared");
}
if(numberPoints<4){
throw new IllegalStateException("Too few points");
}
double x = boundingBox.getMinX(); // base x
double dx = boundingBox.getMaxX()-x;
double y = boundingBox.getMinY(); // base y
double dy = boundingBox.getMaxY()-y;
Polygon p = null;
for(int i=0;i<RUNS;i++){
switch(getGenerationAlgorithm()){
case BOX:
p = createBox(x,dx,y,dy,numberHoles,numberPoints,geometryFactory);
break;
case ARC:
p = createArc(x,dx,y,dy,numberHoles,numberPoints,geometryFactory);
break;
default:
throw new IllegalStateException("Invalid Alg. Specified");
}
IsValidOp valid = new IsValidOp(p);
if(valid.isValid()){
return p;
}
}
return null;
}
private static Polygon createArc(double x, double dx, double y, double dy, int nholes, int npoints, GeometryFactory gf){
// make outer ring first
double radius = dx<dy?dx/3:dy/3;
double cx = x+(dx/2); // center
double cy = y+(dy/2); // center
LinearRing outer = createArc(cx,cy,radius,npoints,gf);
if(nholes == 0){
return gf.createPolygon(outer,null);
}
LinearRing[] inner = new LinearRing[nholes];
radius *= .75;
int degreesPerHole = 360/(nholes+1);
int degreesPerGap = degreesPerHole/nholes;
degreesPerGap = degreesPerGap<2?2:degreesPerGap;
degreesPerHole = (360-(degreesPerGap*nholes))/nholes;
if(degreesPerHole < 2)
throw new RuntimeException("Slices too small for poly. Use Box alg.");
int start = degreesPerGap/2;
for(int i=0;i<nholes;i++){
int st = start+(i*(degreesPerHole+degreesPerGap)); // start angle
inner[i] = createTri(cx,cy,st,st+degreesPerHole,radius,gf);
}
return gf.createPolygon(outer,inner);
}
private static LinearRing createTri(double cx, double cy ,int startAngle, int endAngle, double radius, GeometryFactory gf){
Coordinate[] coords = new Coordinate[4];
double fx1,fx2,fy1,fy2;
double angle = Math.toRadians(startAngle);
fx1 = Math.sin(angle)*radius; // may be neg.
fy1 = Math.cos(angle)*radius; // may be neg.
angle = Math.toRadians(endAngle);
fx2 = Math.sin(angle)*radius; // may be neg.
fy2 = Math.cos(angle)*radius; // may be neg.
coords[0] = new Coordinate(cx,cy);
gf.getPrecisionModel().makePrecise(coords[0]);
coords[1] = new Coordinate(cx+fx1,cy+fy1);
gf.getPrecisionModel().makePrecise(coords[1]);
coords[2] = new Coordinate(cx+fx2,cy+fy2);
gf.getPrecisionModel().makePrecise(coords[2]);
coords[3] = new Coordinate(cx,cy);
gf.getPrecisionModel().makePrecise(coords[3]);
return gf.createLinearRing(coords);
}
private static LinearRing createArc(double cx, double cy ,double radius, int npoints, GeometryFactory gf){
Coordinate[] coords = new Coordinate[npoints+1];
double theta = 360/npoints;
for(int i=0;i<npoints;i++){
double angle = Math.toRadians(theta*i);
double fx = Math.sin(angle)*radius; // may be neg.
double fy = Math.cos(angle)*radius; // may be neg.
coords[i] = new Coordinate(cx+fx,cy+fy);
gf.getPrecisionModel().makePrecise(coords[i]);
}
coords[npoints] = new Coordinate(coords[0]);
gf.getPrecisionModel().makePrecise(coords[npoints]);
return gf.createLinearRing(coords);
}
private static Polygon createBox(double x, double dx, double y, double dy, int nholes, int npoints, GeometryFactory gf){
// make outer ring first
LinearRing outer = createBox(x,dx,y,dy,npoints,gf);
if(nholes == 0){
return gf.createPolygon(outer,null);
}
LinearRing[] inner = new LinearRing[nholes];
int nrow = (int)Math.sqrt(nholes);
int ncol = nholes/nrow;
double ddx = dx/(ncol+1);
double ddy = dy/(nrow+1);
// spacers
double spx = ddx/(ncol+1);
double spy = ddy/(nrow+1);
// should have more grids than required
int cindex = 0;
for(int i=0;i<nrow;i++){
for(int j=0;j<ncol;j++){
if(cindex<nholes){
// make another box
int pts = npoints/2;
pts = pts<4?4:pts;
inner[cindex++] = createBox(spx+x+j*(ddx+spx),ddx,spy+y+i*(ddy+spy),ddy,pts,gf);
}
}
}
return gf.createPolygon(outer,inner);
}
private static LinearRing createBox(double x, double dx, double y, double dy, int npoints, GeometryFactory gf){
//figure out the number of points per side
int ptsPerSide = npoints/4;
int rPtsPerSide = npoints%4;
Coordinate[] coords = new Coordinate[npoints+1];
coords[0] = new Coordinate(x,y); // start
gf.getPrecisionModel().makePrecise(coords[0]);
int cindex = 1;
for(int i=0;i<4;i++){ // sides
int npts = ptsPerSide+(rPtsPerSide-->0?1:0);
// npts atleast 1
if(i%2 == 1){ // odd vert
double cy = dy/npts;
if(i > 1) // down
cy *=-1;
double tx = coords[cindex-1].x;
double sy = coords[cindex-1].y;
for(int j=0;j<npts;j++){
coords[cindex] = new Coordinate(tx,sy+(j+1)*cy);
gf.getPrecisionModel().makePrecise(coords[cindex++]);
}
}else{ // even horz
double cx = dx/npts;
if(i > 1) // down
cx *=-1;
double ty = coords[cindex-1].y;
double sx = coords[cindex-1].x;
for(int j=0;j<npts;j++){
coords[cindex] = new Coordinate(sx+(j+1)*cx,ty);
gf.getPrecisionModel().makePrecise(coords[cindex++]);
}
}
}
coords[npoints] = new Coordinate(x,y); // end
gf.getPrecisionModel().makePrecise(coords[npoints]);
return gf.createLinearRing(coords);
}
/**
* @return Returns the generationAlgorithm.
*/
public int getGenerationAlgorithm() {
return generationAlgorithm;
}
/**
* @param generationAlgorithm The generationAlgorithm to set.
*/
public void setGenerationAlgorithm(int generationAlgorithm) {
this.generationAlgorithm = generationAlgorithm;
}
/**
* @return Returns the numberHoles.
*/
public int getNumberHoles() {
return numberHoles;
}
/**
* @param numberHoles The numberHoles to set.
*/
public void setNumberHoles(int numberHoles) {
this.numberHoles = numberHoles;
}
/**
* @return Returns the numberPoints.
*/
public int getNumberPoints() {
return numberPoints;
}
/**
* @param numberPoints The numberPoints to set.
*/
public void setNumberPoints(int numberPoints) {
this.numberPoints = numberPoints;
}
}