kopia lustrzana https://github.com/onthegomap/planetiler
128 wiersze
4.0 KiB
Java
128 wiersze
4.0 KiB
Java
package com.onthegomap.planetiler.geo;
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import java.util.ArrayList;
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import java.util.List;
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import javax.annotation.concurrent.ThreadSafe;
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import org.locationtech.jts.geom.Geometry;
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import org.locationtech.jts.geom.GeometryCollection;
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import org.locationtech.jts.geom.Point;
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import org.locationtech.jts.geom.Polygon;
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import org.locationtech.jts.index.strtree.STRtree;
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/**
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* Index to efficiently query which polygons contain a point.
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* <p>
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* Writes and reads are thread-safe, but all writes must occur before reads.
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*
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* @param <T> the type of value associated with each polygon
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*/
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@ThreadSafe
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public class PolygonIndex<T> {
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private record GeomWithData<T> (Polygon poly, T data) {}
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private final STRtree index = new STRtree();
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private PolygonIndex() {}
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public static <T> PolygonIndex<T> create() {
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return new PolygonIndex<>();
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}
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private volatile boolean built = false;
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private void build() {
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if (!built) {
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synchronized (this) {
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if (!built) {
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index.build();
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built = true;
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}
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}
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}
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}
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/** Returns the data associated with the first polygon containing {@code point}. */
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public T getOnlyContaining(Point point) {
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List<T> result = getContaining(point);
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return result.isEmpty() ? null : result.get(0);
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}
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/** Returns the data associated with all polygons containing {@code point}. */
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public List<T> getContaining(Point point) {
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build();
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// first pre-filter polygons with envelope that overlaps this point
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List<?> items = index.query(point.getEnvelopeInternal());
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// then post-filter to only polygons that actually contain the point
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return postFilterContaining(point, items);
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}
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private List<T> postFilterContaining(Point point, List<?> items) {
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List<T> result = new ArrayList<>(items.size());
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for (Object item : items) {
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if (item instanceof GeomWithData<?> value && value.poly.contains(point)) {
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@SuppressWarnings("unchecked") T t = (T) value.data;
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result.add(t);
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}
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}
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return result;
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}
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/**
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* Returns the data associated with either the polygons that contain {@code point} or if none are found than the
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* nearest polygon to {@code point} with an envelope that contains point.
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*/
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public List<T> getContainingOrNearest(Point point) {
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build();
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List<?> items = index.query(point.getEnvelopeInternal());
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// optimization: if there's only one then skip checking contains/distance
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if (items.size() == 1) {
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if (items.get(0)instanceof GeomWithData<?> value) {
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@SuppressWarnings("unchecked") T t = (T) value.data;
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return List.of(t);
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}
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}
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List<T> result = postFilterContaining(point, items);
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// if none contain, then look for the nearest polygon from potential overlaps
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if (result.isEmpty()) {
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double nearest = Double.MAX_VALUE;
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T nearestValue = null;
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for (Object item : items) {
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if (item instanceof GeomWithData<?> value) {
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double distance = value.poly.distance(point);
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if (distance < nearest) {
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@SuppressWarnings("unchecked") T t = (T) value.data;
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nearestValue = t;
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nearest = distance;
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}
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}
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}
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if (nearestValue != null) {
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result.add(nearestValue);
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}
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}
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return result;
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}
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/** Returns the data associated with a polygon that contains {@code point} or nearest polygon if none are found. */
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public T get(Point point) {
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List<T> nearests = getContainingOrNearest(point);
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return nearests.isEmpty() ? null : nearests.get(0);
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}
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/** Indexes {@code item} for all polygons contained in {@code geom}. */
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public void put(Geometry geom, T item) {
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if (geom instanceof Polygon poly) {
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// need to externally synchronize inserts into the STRTree
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synchronized (this) {
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index.insert(poly.getEnvelopeInternal(), new GeomWithData<>(poly, item));
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}
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} else if (geom instanceof GeometryCollection geoms) {
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for (int i = 0; i < geoms.getNumGeometries(); i++) {
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put(geoms.getGeometryN(i), item);
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}
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}
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}
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}
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