Implement YStripesPointInAreaLocator

modules/core/src/main/java/org/locationtech/jts/algorithm/locate/YStripesPointInAreaLocator.java

@@ -0,0 +1,129 @@
+package org.locationtech.jts.algorithm.locate;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.Envelope;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.geom.GeometryCollection;
+import org.locationtech.jts.geom.Location;
+import org.locationtech.jts.geom.Polygon;
+import org.locationtech.jts.index.strtree.STRtree;
+
+/**
+ * Point-in-area locator for areal Geometries that uses per-polygon Y-stripe
+ * locators to test points efficiently.
+ * <p>
+ * Each polygonal component of the input Geometry is handled by a
+ * YStripesPointInPolygonLocator; when multiple polygonal components are present
+ * these per-polygon locators are organized in an STRtree for efficient
+ * candidate selection. A single-polygon input uses a direct fast-path, and
+ * geometries with no polygonal elements always report EXTERIOR.
+ * <p>
+ * Instances are immutable and safe for concurrent use, and are intended for
+ * repeated point-in-area queries against a fixed Geometry.
+ * 
+ * @author Michael Carleton
+ * @see YStripesPointInPolygonLocator
+ */
+public final class YStripesPointInAreaLocator implements PointOnGeometryLocator {
+	private final Envelope env;
+	private final PointOnGeometryLocator single;
+	private final STRtree tree; // items are PointOnGeometryLocator
+	private Envelope qEnv = new Envelope(0, 0, 0, 0);
+
+	public YStripesPointInAreaLocator(Geometry geom) {
+		List<Polygon> polys = new ArrayList<>();
+		collectPolygons(geom, polys);
+
+		if (polys.isEmpty()) {
+			this.env = geom.getEnvelopeInternal();
+			this.single = null;
+			this.tree = null;
+			return;
+		}
+
+		if (polys.size() == 1) {
+			this.single = new YStripesPointInPolygonLocator(polys.get(0));
+			this.env = null;
+			this.tree = null;
+			return;
+		}
+
+		Envelope e = new Envelope();
+		STRtree t = new STRtree();
+		for (Polygon p : polys) {
+			Envelope pe = p.getEnvelopeInternal();
+			e.expandToInclude(pe);
+			t.insert(pe, new YStripesPointInPolygonLocator(p));
+		}
+		t.build();
+
+		this.env = e;
+		this.single = null;
+		this.tree = t;
+	}
+
+	/**
+	 * Determines the {@link Location} of a point in an areal {@link Geometry}.
+	 * 
+	 * @param p the point to test
+	 * @return the location of the point in the geometry
+	 */
+	@Override
+	public int locate(Coordinate p) {
+		final double x = p.x, y = p.y;
+
+		// no polygonal elements
+		if (single == null && tree == null) {
+			return Location.EXTERIOR;
+		}
+
+		// single polygon fast-path
+		if (single != null) {
+			return single.locate(p);
+		}
+
+		// global envelope reject
+		if (!env.contains(x, y)) {
+			return Location.EXTERIOR;
+		}
+
+		// STRtree candidate lookup
+		qEnv.init(p);
+		@SuppressWarnings("unchecked")
+		List<PointOnGeometryLocator> cands = tree.query(qEnv);
+
+		if (cands.isEmpty()) {
+			return Location.EXTERIOR;
+		}
+
+		boolean onBoundary = false;
+		for (PointOnGeometryLocator loc : cands) {
+			int l = loc.locate(p);
+			if (l == Location.INTERIOR) {
+				return Location.INTERIOR; // interior dominates
+			}
+			if (l == Location.BOUNDARY) {
+				onBoundary = true;
+			}
+		}
+		return onBoundary ? Location.BOUNDARY : Location.EXTERIOR;
+	}
+
+	private static void collectPolygons(Geometry g, List<Polygon> out) {
+		if (g instanceof Polygon) {
+			if (!g.isEmpty()) {
+				out.add((Polygon) g);
+			}
+			return;
+		}
+		if (g instanceof GeometryCollection) {
+			GeometryCollection gc = (GeometryCollection) g;
+			for (int i = 0; i < gc.getNumGeometries(); i++) {
+				collectPolygons(gc.getGeometryN(i), out);
+			}
+		}
+	}
+}