SmallestSurroundingRectangle.java

package org.wheelmap.android.tango.mode.math;

import com.vividsolutions.jts.algorithm.ConvexHull;
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.Polygon;

import org.rajawali3d.math.vector.Vector2;

import java.util.List;

/**
 * @author julien Gaffuri
 *         (modified) https://sourceforge.net/p/opencarto/code/HEAD/tree/trunk/server/src/main/java/org/opencarto/algo/base/SmallestSurroundingRectangle.java
 */
public class SmallestSurroundingRectangle {

    public static Polygon get(List<Vector2> points) {
        GeometryFactory geometryFactory = new GeometryFactory();

        Coordinate[] coordinates = new Coordinate[points.size() + 1];
        for (int i = 0; i < points.size(); i++) {
            Vector2 v = points.get(i);
            coordinates[i] = new Coordinate(v.getX(), v.getY(), 0);
        }
        // close polygon
        coordinates[coordinates.length - 1] = coordinates[0];
        return get(geometryFactory.createPolygon(coordinates));
    }

    public static Polygon get(Geometry geom) {
        return get(geom, geom.getFactory());
    }

    public static Polygon get(Geometry geom, GeometryFactory gf) {
        Geometry hull_ = (new ConvexHull(geom)).getConvexHull();
        if (!(hull_ instanceof Polygon)) return null;
        Polygon convHull = (Polygon) hull_;

        Coordinate c = geom.getCentroid().getCoordinate();
        Coordinate[] coords = convHull.getExteriorRing().getCoordinates();

        double minArea = Double.MAX_VALUE, minAngle = 0.0;
        Polygon ssr = null;
        Coordinate ci = coords[0], cii;
        for (int i = 0; i < coords.length - 1; i++) {
            cii = coords[i + 1];
            double angle = Math.atan2(cii.y - ci.y, cii.x - ci.x);
            Polygon rect = (Polygon) Rotation.get(convHull, c, -1.0 * angle, gf).getEnvelope();
            double area = rect.getArea();
            if (area < minArea) {
                minArea = area;
                ssr = rect;
                minAngle = angle;
            }
            ci = cii;
        }
        return Rotation.get(ssr, c, minAngle, gf);
    }

    public static Polygon get(Geometry geom, boolean preserveSize) {
        return get(geom, geom.getFactory(), preserveSize);
    }

    public static Polygon get(Geometry geom, GeometryFactory gf, boolean preserveSize) {
        if (!preserveSize) return get(geom, gf);

        Polygon out = get(geom, gf);
        double ini = geom.getArea();
        double fin = out.getArea();

        if (fin == 0) {
            return out;
        }

        return Scaling.get(out, out.getCentroid().getCoordinate(), Math.sqrt(ini / fin), gf);
    }

}