ST_MakeGrid.java

/**
 * H2GIS is a library that brings spatial support to the H2 Database Engine
 * <http://www.h2database.com>. H2GIS is developed by CNRS
 * <http://www.cnrs.fr/>.
 *
 * This code is part of the H2GIS project. H2GIS 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;
 * version 3.0 of the License.
 *
 * H2GIS 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 <http://www.gnu.org/licenses/>.
 *
 *
 * For more information, please consult: <http://www.h2gis.org/>
 * or contact directly: info_at_h2gis.org
 */

package org.h2gis.functions.spatial.create;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.h2.value.Value;
import org.h2.value.ValueGeometry;
import org.h2.value.ValueString;
import org.h2gis.api.AbstractFunction;
import static org.h2gis.api.Function.PROP_REMARKS;
import org.h2gis.api.ScalarFunction;
import static org.h2gis.api.ScalarFunction.PROP_NOBUFFER;

/**
 * Create a regular grid based on a table or a geometry envelope. The geometry
 * envelope could be expressed using a subquery as 
 * (SELECT the_geom from myTable)
 *
 * @author Erwan Bocher
 */
public class ST_MakeGrid extends AbstractFunction implements ScalarFunction {

  
    public ST_MakeGrid() {
        addProperty(PROP_REMARKS, "Calculate a regular grid.\n"
                + "The first argument is either a geometry or a table.\n"
                + "The delta X and Y cell grid are expressed in a cartesian plane."
                + "Note :The geometry could be expressed using a subquery as\n"
                + " (SELECT the_geom from myTable)");
        addProperty(PROP_NOBUFFER, true);
    }

    @Override
    public String getJavaStaticMethod() {
        return "createGrid";
    }

    /**
     * Create a regular grid using the first input argument to compute the full
     * extent.
     *
     * @param connection
     * @param value could be the name of a table or a geometry.
     * @param deltaX the X cell size
     * @param deltaY the Y cell size
     * @return a resultset that contains all cells as a set of polygons
     * @throws SQLException
     */
    public static ResultSet createGrid(Connection connection, Value value, double deltaX, double deltaY) throws SQLException {
        if(value == null){
            return null;
        }
        if (value instanceof ValueString) {
            GridRowSet gridRowSet = new GridRowSet(connection, deltaX, deltaY, value.getString());
            return gridRowSet.getResultSet();
        } else if (value instanceof ValueGeometry) {
            ValueGeometry geom = (ValueGeometry) value;
            GridRowSet gridRowSet = new GridRowSet(connection, deltaX, deltaY, geom.getGeometry().getEnvelopeInternal());
            return gridRowSet.getResultSet();
        } else {
            throw new SQLException("This function supports only table name or geometry as first argument.");
        }
    }
}