Subversion Repositories mkgmap

/*
 * Copyright (C) 2013.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 or
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */
 
package uk.me.parabola.mkgmap.filters;

import uk.me.parabola.imgfmt.app.Coord;
import uk.me.parabola.imgfmt.app.trergn.Subdivision;
import uk.me.parabola.mkgmap.general.MapElement;
import uk.me.parabola.mkgmap.general.MapLine;
import uk.me.parabola.mkgmap.general.MapShape;

/**
 * This filter does more or less the same calculations as LinePreparer.calcDeltas  
 * It rejects lines that have not enough different points
 * @author GerdP
 *
 */
public class LinePreparerFilter implements MapFilter {

        private int shift;
        private final Subdivision subdiv;

        public LinePreparerFilter(Subdivision subdiv) {
                this.subdiv = subdiv;
        }

        public void init(FilterConfig config) {
                shift = config.getShift();
        }

        /**
         * @param element A map element that will be a line or a polygon.
         * @param next This is used to pass the (unchanged) element onward.
         */
        public void doFilter(MapElement element, MapFilterChain next) {
                MapLine line = (MapLine) element;

                boolean first = true;
                int minPointsRequired = (element instanceof MapShape) ? 3:2;

                int lastLat = 0;
                int lastLong = 0;
                int numPointsEncoded = 1;
                for (int i = 0; i < line.getPoints().size(); i++) {
                        Coord co = line.getPoints().get(i);

                        int lat = subdiv.roundLatToLocalShifted(co.getLatitude());
                        int lon = subdiv.roundLonToLocalShifted(co.getLongitude());
                       
                        if (first) {
                                lastLat = lat;
                                lastLong = lon;
                                first = false;
                                continue;
                        }

                        // compute normalized differences
                        //   -2^(shift-1) <= dx, dy < 2^(shift-1)
                        // XXX: relies on the fact that java integers are 32 bit signed
                        final int offset = 8+shift;
                        int dx = (lon - lastLong) << offset >> offset;
                        int dy = (lat - lastLat) << offset >> offset;
                        if (dx == 0 && dy == 0)
                                continue;
                               
                        ++numPointsEncoded;
                        if (numPointsEncoded >= minPointsRequired)
                                break;
                        lastLong = lon;
                        lastLat = lat;
                }              
                if(numPointsEncoded < minPointsRequired)
                        return;
               
                next.doFilter(element);
        }
}