GeometryMapper.java
/*
* Copyright (c) 2016 Martin Davis.
*
* 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.geom.util;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryCollection;
/**
* Methods to map various collections
* of {@link Geometry}s
* via defined mapping functions.
*
* @author Martin Davis
*
*/
public class GeometryMapper
{
/**
* Maps the members of a {@link Geometry}
* (which may be atomic or composite)
* into another <tt>Geometry</tt> of most specific type.
* <tt>null</tt> results are skipped.
* In the case of hierarchical {@link GeometryCollection}s,
* only the first level of members are mapped.
*
* @param geom the input atomic or composite geometry
* @param op the mapping operation
* @return a result collection or geometry of most specific type
*/
public static Geometry map(Geometry geom, MapOp op)
{
List mapped = new ArrayList();
for (int i = 0; i < geom.getNumGeometries(); i++) {
Geometry g = op.map(geom.getGeometryN(i));
if (g != null)
mapped.add(g);
}
return geom.getFactory().buildGeometry(mapped);
}
public static Collection map(Collection geoms, MapOp op)
{
List mapped = new ArrayList();
for (Iterator i = geoms.iterator(); i.hasNext(); ) {
Geometry g = (Geometry) i.next();
Geometry gr = op.map(g);
if (gr != null)
mapped.add(gr);
}
return mapped;
}
/**
* Maps the atomic elements of a {@link Geometry}
* (which may be atomic or composite)
* using a {@link MapOp} mapping operation
* into an atomic <tt>Geometry</tt> or a flat collection
* of the most specific type.
* <tt>null</tt> and empty values returned from the mapping operation
* are discarded.
*
* @param geom the geometry to map
* @param emptyDim the dimension of empty geometry to create
* @param op the mapping operation
* @return the mapped result
*/
public static Geometry flatMap(Geometry geom, int emptyDim, MapOp op)
{
List<Geometry> mapped = new ArrayList<Geometry>();
flatMap(geom, op, mapped);
if (mapped.size() == 0) {
return geom.getFactory().createEmpty(emptyDim);
}
if (mapped.size() == 1)
return mapped.get(0);
return geom.getFactory().buildGeometry(mapped);
}
private static void flatMap(Geometry geom, MapOp op, List<Geometry> mapped)
{
for (int i = 0; i < geom.getNumGeometries(); i++) {
Geometry g = geom.getGeometryN(i);
if (g instanceof GeometryCollection) {
flatMap(g, op, mapped);
}
else {
Geometry res = op.map(g);
if (res != null && ! res.isEmpty()) {
addFlat(res, mapped);
}
}
}
}
private static void addFlat(Geometry geom, List<Geometry> geomList) {
if (geom.isEmpty()) return;
if (geom instanceof GeometryCollection) {
for (int i = 0; i < geom.getNumGeometries(); i++) {
addFlat(geom.getGeometryN(i), geomList);
}
}
else {
geomList.add(geom);
}
}
/**
* An interface for geometry functions that map a geometry input to a geometry output.
* The output may be <tt>null</tt> if there is no valid output value for
* the given input value.
*
* @author Martin Davis
*
*/
public interface MapOp
{
/**
* Maps a geometry value into another value.
*
* @param geom the input geometry
* @return a result geometry
*/
Geometry map(Geometry geom);
}
}