GeoJsonTileDecoder.java

/*
 * Copyright 2014 Hannes Janetzek
 *
 * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
 *
 * This program is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */
package org.oscim.tiling.source.geojson;

import static org.oscim.core.MercatorProjection.latitudeToY;
import static org.oscim.core.MercatorProjection.longitudeToX;

import java.io.IOException;
import java.io.InputStream;
import java.util.LinkedHashMap;

import org.oscim.core.GeometryBuffer.GeometryType;
import org.oscim.core.MapElement;
import org.oscim.core.Tile;
import org.oscim.tiling.ITileDataSink;
import org.oscim.tiling.source.ITileDecoder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.gwt.core.client.JavaScriptObject;

public class GeoJsonTileDecoder implements ITileDecoder {
	static final Logger log = LoggerFactory.getLogger(GeoJsonTileDecoder.class);

	private final MapElement mapElement;
	private final GeoJsonTileSource mTileSource;

	private ITileDataSink mTileDataSink;

	public GeoJsonTileDecoder(GeoJsonTileSource tileSource) {
		mTileSource = tileSource;
		mapElement = new MapElement();
		mapElement.layer = 5;
	}

	final static LinkedHashMap<String, Object> mProperties = new LinkedHashMap<String, Object>(10);

	double mTileY, mTileX, mTileScale;

	public boolean decode(Tile tile, ITileDataSink sink, JavaScriptObject jso) {
		mTileDataSink = sink;

		mTileScale = 1 << tile.zoomLevel;
		mTileX = tile.tileX / mTileScale;
		mTileY = tile.tileY / mTileScale;
		mTileScale *= Tile.SIZE;

		FeatureCollection c = (FeatureCollection) jso;

		for (Feature f : c.getFeatures()) {
			mapElement.clear();
			mapElement.tags.clear();

			/* add tag information */
			mTileSource.decodeTags(mapElement, f.getProperties(mProperties));
			if (mapElement.tags.numTags == 0)
				continue;

			/* add geometry information */
			decodeGeometry(f.getGeometry());

			if (mapElement.type == GeometryType.NONE)
				continue;

			mTileDataSink.process(mapElement);
		}

		return true;
	}

	private void decodeGeometry(Geometry<?> geometry) {
		String type = geometry.type();

		if ("Polygon".equals(type)) {
			Polygon p = (Polygon) geometry.getCoordinates();
			decodePolygon(p);
		} else if ("MultiPolygon".equals(type)) {
			MultiPolygon mp = (MultiPolygon) geometry.getCoordinates();
			for (int k = 0, l = mp.getNumGeometries(); k < l; k++)
				decodePolygon(mp.getGeometryN(k));

		} else if ("LineString".equals(type)) {
			LineString ls = (LineString) geometry.getCoordinates();
			decodeLineString(ls);

		} else if ("MultiLineString".equals(type)) {
			MultiLineString ml = (MultiLineString) geometry.getCoordinates();
			for (int k = 0, n = ml.getNumGeometries(); k < n; k++)
				decodeLineString(ml.getGeometryN(k));
		}
	}

	private void decodeLineString(LineString l) {
		mapElement.startLine();
		for (int j = 0, m = l.length(); j < m; j++) {
			decodePoint(l.get(j));
		}
	}

	private void decodePolygon(Polygon p) {
		for (int i = 0, n = p.getNumRings(); i < n; i++) {
			if (i > 0)
				mapElement.startHole();
			else
				mapElement.startPolygon();

			LineString ls = p.getRing(i);
			for (int j = 0, m = ls.length() - 1; j < m; j++)
				decodePoint(ls.get(j));
		}
	}

	private void decodePoint(LngLat point) {

		float x = (float) ((longitudeToX(point.getLongitude()) - mTileX) * mTileScale);
		float y = (float) ((latitudeToY(point.getLatitude()) - mTileY) * mTileScale);

		mapElement.addPoint(x, y);
	}

	@Override
	public boolean decode(Tile tile, ITileDataSink sink, InputStream is) throws IOException {
		return false;
	}
}