package org.osm2world.core.math.algorithms;
import static org.osm2world.core.math.JTSConversionUtil.polygonXZToJTSPolygon;
import static org.osm2world.core.math.JTSConversionUtil.polygonsXZFromJTSGeometry;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import org.osm2world.core.math.PolygonWithHolesXZ;
import org.osm2world.core.math.SimplePolygonXZ;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryCollection;
import com.vividsolutions.jts.geom.Polygon;
/**
* utility class for Constructive Area Geometry (CAG),
* boolean operations on areas
*/
public final class CAGUtil {
private CAGUtil() { }
/**
* takes a polygon outline, "subtracts" a collection of other polygon outlines,
* and returns a collection of polygons that covers the difference area.
*
* The result polygons should cover the area that was
* within the original polygon (excluding its holes),
* but not within a subtracted polygon.
*
* @return
* polygons without self-intersections, but maybe with holes
*/
public static final Collection<PolygonWithHolesXZ> subtractPolygons(
SimplePolygonXZ basePolygon,
List<? extends SimplePolygonXZ> subtractPolygons) {
List<Geometry> remainingGeometry = Collections.singletonList(
(Geometry)polygonXZToJTSPolygon(basePolygon));
for (SimplePolygonXZ subtractPolygon : subtractPolygons) {
List<Geometry> newRemainingGeometry = new ArrayList<Geometry>(1);
for (Geometry g : remainingGeometry) {
Geometry newG = g.difference(
polygonXZToJTSPolygon(subtractPolygon));
if (newG instanceof GeometryCollection) {
for (int i = 0; i < ((GeometryCollection)newG).getNumGeometries(); i++) {
newRemainingGeometry.add(((GeometryCollection)newG).getGeometryN(i));
}
} else {
newRemainingGeometry.add(newG);
}
}
remainingGeometry = newRemainingGeometry;
}
Collection<PolygonWithHolesXZ> result =
new ArrayList<PolygonWithHolesXZ>();
for (Geometry g : remainingGeometry) {
result.addAll(polygonsXZFromJTSGeometry(g));
}
return result;
}
/**
* calculates the intersection area of a collection of polygons.
*
* The result polygons should cover the area that was
* within all of the polygons.
*/
public static final Collection<PolygonWithHolesXZ> intersectPolygons(
List<? extends SimplePolygonXZ> intersectPolygons) {
if (intersectPolygons.isEmpty()) { throw new IllegalArgumentException(); }
Geometry remainingGeometry = null;
for (SimplePolygonXZ poly : intersectPolygons) {
Polygon jtsPoly = polygonXZToJTSPolygon(poly);
if (remainingGeometry == null) {
remainingGeometry = jtsPoly;
} else {
remainingGeometry = remainingGeometry.intersection(jtsPoly);
}
}
return polygonsXZFromJTSGeometry(remainingGeometry);
}
}