TileInfo.java :  » Tools » mapsforge » org » mapsforge » preprocessing » map » osmosis » Android Open Source

/*
 * Copyright 2010, 2011 mapsforge.org
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.mapsforge.preprocessing.map.osmosis;

import java.io.DataInputStream;
import java.io.IOException;
import java.util.BitSet;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

final class TileInfo {

  private static final Logger LOGGER =
      Logger.getLogger(TileInfo.class.getName());

  private static final byte SEA = 0x2;

  static final byte TILE_INFO_ZOOMLEVEL = 0xC;

  private static final byte BITMASK = 0x3;

  // 4096 * 4096 / 4 (2 bits for each tile)
  private static final int N_BYTES = 0x400000;
  // 4096 * 4096 = number of tiles on zoom level 12
  private static final int N_BITS = 0x1000000;

  private final BitSet seaTileInfo = new BitSet(N_BITS);

  private TileInfo(String strInputFile) {
    try {

      DataInputStream dis = new DataInputStream(
          TileInfo.class.getClassLoader().getResourceAsStream(strInputFile));
      byte currentByte;

      long start = System.currentTimeMillis();
      for (int i = 0; i < N_BYTES; i++) {
        currentByte = dis.readByte();
        if (((currentByte >> 6) & BITMASK) == SEA) {
          seaTileInfo.set(i * 4);
        }
        if (((currentByte >> 4) & BITMASK) == SEA) {
          seaTileInfo.set(i * 4 + 1);
        }
        if (((currentByte >> 2) & BITMASK) == SEA) {
          seaTileInfo.set(i * 4 + 2);
        }
        if ((currentByte & BITMASK) == SEA) {
          seaTileInfo.set(i * 4 + 3);
        }
      }
      LOGGER.fine("loading of tile info data took "
          + (System.currentTimeMillis() - start)
          + " ms");
    } catch (IOException e) {
      LOGGER.log(Level.SEVERE, "error loading tile info from file " + strInputFile);
    }
  }

  static TileInfo getInstance() {
    return new TileInfo("org/mapsforge/preprocessing/map/osmosis/oceantiles_12.dat");
  }

  /**
   * Checks if a tile is completely covered by water. <b>Important notice:</b> The method may
   * produce false negatives on higher zoom levels than 12.
   * 
   * @param tc
   *            tile given as TileCoordinate
   * @return true if the tile is completely covered by water, false if the associated tile(s)
   *         on zoom level 12 is(are) not completely covered by water.
   */
  boolean isWaterTile(TileCoordinate tc) {
    List<TileCoordinate> tiles = tc.translateToZoomLevel(TILE_INFO_ZOOMLEVEL);
    for (TileCoordinate tile : tiles) {
      if (!seaTileInfo.get(tile.getY() * 4096 + tile.getX()))
        return false;
    }
    return true;
  }
}