LineSizeSplitterFilter.java

/*
 * Copyright (C) 2007 Steve Ratcliffe
 * 
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License 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.
 * 
 * 
 * Author: Steve Ratcliffe
 * Create date: Dec 1, 2007
 */
package uk.me.parabola.mkgmap.filters;

import java.util.ArrayList;
import java.util.List;

import uk.me.parabola.imgfmt.app.Coord;
import uk.me.parabola.log.Logger;
import uk.me.parabola.mkgmap.general.MapElement;
import uk.me.parabola.mkgmap.general.MapLine;
import uk.me.parabola.mkgmap.general.MapRoad;
import uk.me.parabola.mkgmap.general.MapShape;

/**
 * A filter to make sure that a line does not have a greater dimension that
 * would cause an overflow of a TRE area which can only have 15 bits of
 * size.  We want to keep things well under this.
 *
 * @author Steve Ratcliffe
 */
public class LineSizeSplitterFilter implements MapFilter {
	private static final Logger log = Logger.getLogger(LineSizeSplitterFilter.class);

	public static final int MAX_SIZE = 0x7fff;

	private int maxSize;

	public void init(FilterConfig config) {
		int shift = config.getShift();
		if (shift > 15)
			shift = 16;
		maxSize = Math.min((1<<24)-1, Math.max(MAX_SIZE << shift, 0x8000));		
	}

	// return the greater of the absolute values of HEIGHT and WIDTH
	// divided by the maximum allowed size - so if the height and
	// width are not too large, the result will be <= 1.0
	public static double testDims(int height, int width) {
		return (double)Math.max(Math.abs(height), Math.abs(width)) / MAX_SIZE;
	}

	/**
	 * Keep track of the max dimensions of a line and split when they get too
	 * big.
	 *
	 * @param element A map element.
	 * @param next This is used to pass the possibly transformed element onward.
	 */
	public void doFilter(MapElement element, MapFilterChain next) {
		// We do not deal with shapes.
		assert !(element instanceof MapShape) && element instanceof MapLine;

		MapLine line = (MapLine) element;

		if (line.getBounds().getMaxDimension() < maxSize) {
			next.doFilter(element);
			return;
		}

		if(line instanceof MapRoad) {
			MapRoad road = ((MapRoad)line);
			log.error("Way " + road.getRoadDef() + " has a max dimension of " + line.getBounds().getMaxDimension() + " and is about to be split (routing will be broken)");
		}
		
		// ensure that all single lines do not exceed the maximum size
		// use a slightly decreased max size (-10) to get better results 
		// in the subdivision creation
		List<Coord> points = splitLinesToMaxSize(line.getPoints(), maxSize-10);

		log.debug("line bbox too big, splitting");

		MapLine l = line.copy();

		List<Coord> coords = new ArrayList<Coord>();
		boolean first = true;

		/**
		 * Class to keep track of the dimensions.
		 */
		class Dim {
			private int minLat;
			private int minLong;
			private int maxLat;
			private int maxLong;

			Dim() {
				reset();
			}

			private void reset() {
				minLat = Integer.MAX_VALUE;
				minLong = Integer.MAX_VALUE;
				maxLat = Integer.MIN_VALUE;
				maxLong = Integer.MIN_VALUE;
			}

			private void addToBounds(Coord co) {
				int lat = co.getLatitude();
				if (lat < minLat)
					minLat = lat;
				if (lat > maxLat)
					maxLat = lat;

				int lon = co.getLongitude();
				if (lon < minLong)
					minLong = lon;
				if (lon > maxLong)
					maxLong = lon;
			}

			private int getMaxDim() {
				int dx = maxLong - minLong;
				int dy = maxLat - minLat;
				return Math.max(dx, dy);
			}
		}

		Dim dim = new Dim();
		Coord prev = null;
		
		// Add points while not too big and then start again with a fresh line.
		for (Coord co: points){
			dim.addToBounds(co);
			if (dim.getMaxDim() > maxSize) {
				if (first)
					log.debug("bigness saving first part");
				else 
					log.debug("bigness saving next part");
				l.setPoints(coords);
				next.doFilter(l);

				l = line.copy();

				first = false;
				dim.reset();
				coords = new ArrayList<Coord>();
				coords.add(prev);
				dim.addToBounds(prev);
				dim.addToBounds(co);
			}
			coords.add(co);
			prev = co;
		}
		assert coords.size() > 1;
		if (coords.size() > 1) {
			log.debug("bigness saving a final part");
			l.setPoints(coords);
			next.doFilter(l);
		}
	}
	
	/**
	 * If two points of a line are too far from each other, add points between them
	 * so that the bounding box of each pair of points is smaller than the allowed
	 * maximum.
	 * @param coords the list of points 
	 * @param maxSize the allowed bounding box height and width 
	 * @return a reference to a new list of points 
	 */
	private static List<Coord> splitLinesToMaxSize(List<Coord> coords, int maxSize){
		List<Coord> testedCoords = new ArrayList<Coord>(coords);
		int posToTest = coords.size() -2;
		while (posToTest >= 0){
			Coord p1 = testedCoords.get(posToTest);
			Coord p2 = testedCoords.get(posToTest+1);
			int width = Math.abs( p1.getLongitude() - p2.getLongitude());
			int height = Math.abs( p1.getLatitude() - p2.getLatitude());
			if (width > maxSize || height > maxSize){
				testedCoords.add(posToTest+1, p1.makeBetweenPoint(p2, 0.5));
				++posToTest;
			}
			else
				--posToTest;
		}
		return testedCoords;
	}
}