CircularExtentFilter.java

/**
 * 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 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/>.
 * 
 * @author Arne Kepp, OpenGeo, Copyright 2009
 */
package org.geowebcache.filter.request;

import org.geowebcache.GeoWebCacheException;
import org.geowebcache.conveyor.ConveyorTile;
import org.geowebcache.grid.GridSubset;
import org.geowebcache.layer.TileLayer;

/**
 * This is a test filter for the new request filter core.
 * 
 * It is not really useful other than to illustrate the concept.
 * 
 * Basically it takes the extent of the layer and constructs a
 * a circle that covers half the 
 *
 */
public class CircularExtentFilter extends RequestFilter {

    private static final long serialVersionUID = -8488899568092162423L;

    CircularExtentFilter() {
        
    }
    
    public void apply(ConveyorTile convTile) throws RequestFilterException {
        TileLayer tl = convTile.getLayer();
        //SRS srs = convTile.getSRS(); 
        GridSubset gridSubset = tl.getGridSubset(convTile.getGridSetId());
        
        int z = (int) convTile.getTileIndex()[2];
        long[] gridCoverage = gridSubset.getCoverage(z);

        // Figure out the radius
        long width = gridCoverage[2] - gridCoverage[0];
        long height = gridCoverage[3] - gridCoverage[1];
        
        // Rounding must always err on the side of 
        // caution if you want to use KML hierarchies
        long maxRad = 0;
        if(width > height) {
            maxRad = (width / 4) + 1;
        } else {
            maxRad = (height / 4) + 1;
        }
        
        // Figure out how the requested bounds relate
        long midX = gridCoverage[0] + width/2;
        long midY = gridCoverage[1] + height/2;
        

        long xDist = midX - convTile.getTileIndex()[0];
        long yDist = midY - convTile.getTileIndex()[1];
        
        long rad = Math.round(Math.sqrt(xDist*xDist + yDist*yDist));
        
        if(rad > maxRad) {
            throw new BlankTileException(this);
        }   
    }

    public void initialize(TileLayer layer) throws GeoWebCacheException {
        // Do nothing
    }

    public void update(TileLayer layer, String gridSetId, int zoomStart, int zoomStop) 
    throws GeoWebCacheException {
        // Do nothing
    }
    
    public void update(byte[] filterData, TileLayer layer, String gridSetId, int z)
            throws GeoWebCacheException {
        // Do nothing
    }

    public boolean update(TileLayer layer, String gridSetId) {
        // Do nothing
        return false;
    }
}