source: osm/applications/editors/josm/plugins/utilsplugin/src/UtilsPlugin/SimplifyWayAction.java@ 5427

package UtilsPlugin;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.command.ChangeCommand;
import org.openstreetmap.josm.command.Command;
import org.openstreetmap.josm.command.DeleteCommand;
import org.openstreetmap.josm.command.SequenceCommand;
import org.openstreetmap.josm.data.coor.LatLon;
import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.data.osm.visitor.CollectBackReferencesVisitor;

import org.openstreetmap.josm.data.osm.DataSet;
import org.openstreetmap.josm.actions.JosmAction;

public class SimplifyWayAction extends JosmAction {
        public SimplifyWayAction() {
                super(tr("Simplify Way"), "simplify",
                        tr("Delete unnecessary nodes from a way."), 0, 0, true);
        }

        public void actionPerformed(ActionEvent e) {
                Collection<OsmPrimitive> selection = Main.ds.getSelected();

                if (selection.size() == 1 && selection.iterator().next() instanceof Way) {
                        simplifyWay((Way) selection.iterator().next());
                }
        }

        public void simplifyWay(Way w) {
                double threshold = Double.parseDouble(
                        Main.pref.get("simplify-way.max-error", "50"));

                Way wnew = new Way(w);

                int toI = wnew.nodes.size() - 1;
                for (int i = wnew.nodes.size() - 1; i >= 0; i--) {
                        CollectBackReferencesVisitor backRefsV =
                                new CollectBackReferencesVisitor(Main.ds, false);
                        backRefsV.visit(wnew.nodes.get(i));
                        boolean used = false;
                        if (backRefsV.data.size() == 1) {
                                used = Collections.frequency(
                                        w.nodes, wnew.nodes.get(i)) > 1;
                        } else {
                                backRefsV.data.remove(w);
                                used = !backRefsV.data.isEmpty();
                        }
                        if (!used) used = wnew.nodes.get(i).tagged;

                        if (used) {
                                simplifyWayRange(wnew, i, toI, threshold);
                                toI = i;
                        }
                }
                simplifyWayRange(wnew, 0, toI, threshold);

                HashSet<Node> delNodes = new HashSet<Node>();
                delNodes.addAll(w.nodes);
                delNodes.removeAll(wnew.nodes);

                if (wnew.nodes.size() != w.nodes.size()) {
                        Collection<Command> cmds = new LinkedList<Command>();
                        cmds.add(new ChangeCommand(w, wnew));
                        cmds.add(new DeleteCommand(delNodes));
                        Main.main.undoRedo.add(
                                new SequenceCommand(tr("Simplify Way (remove {0} nodes)",
                                                delNodes.size()),
                                        cmds));
                        Main.map.repaint();
                }
        }

        public void simplifyWayRange(Way wnew, int from, int to, double thr) {
                if (to - from >= 2) {
                        ArrayList<Node> ns = new ArrayList<Node>();
                        simplifyWayRange(wnew, from, to, ns, thr);
                        for (int j = to-1; j > from; j--) wnew.nodes.remove(j);
                        wnew.nodes.addAll(from+1, ns);
                }
        }

        /*
         * Takes an interval [from,to] and adds nodes from the set (from,to) to
         * ns.
         */
        public void simplifyWayRange(Way wnew, int from, int to, ArrayList<Node> ns, double thr) {
                Node fromN = wnew.nodes.get(from), toN = wnew.nodes.get(to);

                int imax = -1;
                double xtemax = 0;
                for (int i = from+1; i < to; i++) {
                        Node n = wnew.nodes.get(i);
                        double xte = Math.abs(EARTH_RAD * xtd(
                                fromN.coor.lat(), fromN.coor.lon(),
                                toN.coor.lat(), toN.coor.lon(),
                                n.coor.lat(), n.coor.lon()));
                        if (xte > xtemax) {
                                xtemax = xte;
                                imax = i;
                        }
                }

                if (imax != -1 && xtemax >= thr) {
                        simplifyWayRange(wnew, from, imax, ns, thr);
                        ns.add(wnew.nodes.get(imax));
                        simplifyWayRange(wnew, imax, to, ns, thr);
                }
        }

        public static double EARTH_RAD = 6378137.0;

        /* From Aviaton Formulary v1.3
         * http://williams.best.vwh.net/avform.htm
         */
        public static double dist(double lat1, double lon1, double lat2, double lon2) {
                return 2*Math.asin(Math.sqrt(Math.pow(Math.sin((lat1-lat2)/2), 2) + 
                        Math.cos(lat1)*Math.cos(lat2)*Math.pow(Math.sin((lon1-lon2)/2), 2)));
        }

        public static double course(double lat1, double lon1, double lat2, double lon2) {
                return Math.atan2(Math.sin(lon1-lon2)*Math.cos(lat2),
                    Math.cos(lat1)*Math.sin(lat2)-Math.sin(lat1)*Math.cos(lat2)*Math.cos(lon1-lon2)) % (2*Math.PI);
        }

        public static double xtd(double lat1, double lon1, double lat2, double lon2, double lat3, double lon3) {
                double dist_AD = dist(lat1, lon1, lat3, lon3);
                double crs_AD = course(lat1, lon1, lat3, lon3);
                double crs_AB = course(lat1, lon1, lat2, lon2);
                return Math.asin(Math.sin(dist_AD)*Math.sin(crs_AD-crs_AB));
        }
}