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/**
* H2GIS is a library that brings spatial support to the H2 Database Engine
* . H2GIS is developed by CNRS
* .
*
* 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 .
*
*
* For more information, please consult:
* or contact directly: info_at_h2gis.org
*/
package org.h2gis.functions.spatial.create;
import com.vividsolutions.jts.geom.*;
import org.h2.tools.SimpleResultSet;
import org.h2.tools.SimpleRowSource;
import org.h2gis.utilities.JDBCUtilities;
import org.h2gis.utilities.SFSUtilities;
import org.h2gis.utilities.TableLocation;
import java.sql.*;
import java.util.List;
/**
* GridRowSet is used to populate a result set with all grid cells. A cell could
* be represented as a polygon or its center point.
*
* @author Erwan Bocher
*/
public class GridRowSet implements SimpleRowSource {
private static final GeometryFactory GF = new GeometryFactory();
private static int cellI = 0;
private static int cellJ = 0;
private int maxI, maxJ;
private double deltaX, deltaY;
private double minX, minY;
private int id = 0;
private final Connection connection;
private boolean firstRow = true;
private Envelope envelope;
private boolean isTable;
private String tableName;
private boolean isCenterCell = false;
/**
* The grid will be computed according a table stored in the database
*
* @param connection
* @param deltaX
* @param deltaY
* @param tableName
*/
public GridRowSet(Connection connection, double deltaX, double deltaY, String tableName) {
this.connection = connection;
this.deltaX = deltaX;
this.deltaY = deltaY;
this.tableName = tableName;
this.isTable = true;
}
/**
* The grid will be computed according an envelope
*
* @param connection
* @param deltaX
* @param deltaY
* @param envelope
*/
public GridRowSet(Connection connection, double deltaX, double deltaY, Envelope envelope) {
this.connection = connection;
this.deltaX = deltaX;
this.deltaY = deltaY;
this.envelope = envelope;
this.isTable = false;
}
@Override
public Object[] readRow() throws SQLException {
if (firstRow) {
reset();
}
if (cellI == maxI) {
cellJ++;
cellI = 0;
}
if (cellJ >= maxJ) {
cellJ = 0;
return null;
}
if (isCenterCell) {
return new Object[]{getCellPoint(), id++, cellI, cellJ + 1};
}
return new Object[]{getCellPolygon(), id++, cellI, cellJ + 1};
}
@Override
public void close() {
}
@Override
public void reset() throws SQLException {
cellI = 0;
cellJ = 0;
firstRow = false;
//We compute the extend according the first input value
if (isTable) {
Statement statement = connection.createStatement();
ResultSet rs = statement.executeQuery("select ST_Extent(" + getFirstGeometryField(tableName, connection) + ") from " + tableName);
try {
rs.next();
Geometry geomExtend = (Geometry) rs.getObject(1);
if (geomExtend == null) {
throw new SQLException("The envelope cannot be null.");
} else {
envelope = geomExtend.getEnvelopeInternal();
initParameters();
}
} finally {
rs.close();
}
} else {
if (envelope == null) {
throw new SQLException("The input geometry used to compute the grid cannot be null.");
} else {
initParameters();
}
}
}
/**
* Compute the polygon corresponding to the cell
*
* @return Polygon of the cell
*/
private Polygon getCellPolygon() {
final Coordinate[] summits = new Coordinate[5];
double x1 = minX + cellI * deltaX;
double y1 = minY + cellJ * deltaY;
double x2 = minX + (cellI + 1) * deltaX;
double y2 = minY + (cellJ + 1) * deltaY;
summits[0] = new Coordinate(x1, y1);
summits[1] = new Coordinate(x2, y1);
summits[2] = new Coordinate(x2, y2);
summits[3] = new Coordinate(x1, y2);
summits[4] = new Coordinate(x1, y1);
final LinearRing g = GF.createLinearRing(summits);
final Polygon gg = GF.createPolygon(g, null);
cellI++;
return gg;
}
/**
* Compute the point of the cell
*
* @return Center point of the cell
*/
private Point getCellPoint() {
double x1 = (minX + cellI * deltaX) + (deltaX / 2d);
double y1 = (minY + cellJ * deltaY) + (deltaY / 2d);
cellI++;
return GF.createPoint(new Coordinate(x1, y1));
}
/**
* Return true is cell is represented as point, false as a polygon
*
* @return
*/
public boolean isCenterCell() {
return isCenterCell;
}
/**
* Set if the cell must be represented as a point or a polygon
*
* @param isCenterCell
*/
public void setCenterCell(boolean isCenterCell) {
this.isCenterCell = isCenterCell;
}
/**
* Return the first spatial geometry field name
*
* @param tableName
* @param connection
* @return the name of the first geometry column
* @throws SQLException
*/
private static String getFirstGeometryField(String tableName, Connection connection) throws SQLException {
// Find first geometry column
List geomFields = SFSUtilities.getGeometryFields(connection, TableLocation.parse(tableName, JDBCUtilities.isH2DataBase(connection.getMetaData())));
if (!geomFields.isEmpty()) {
return geomFields.get(0);
} else {
throw new SQLException("The table " + tableName + " does not contain a geometry field");
}
}
/**
* Compute the parameters need to create each cells
*
*/
private void initParameters() {
this.minX = envelope.getMinX();
this.minY = envelope.getMinY();
double cellWidth = envelope.getWidth();
double cellHeight = envelope.getHeight();
this.maxI = (int) Math.ceil(cellWidth
/ deltaX);
this.maxJ = (int) Math.ceil(cellHeight
/ deltaY);
}
/**
* Give the regular grid
*
* @return ResultSet
* @throws SQLException
*/
public ResultSet getResultSet() throws SQLException {
SimpleResultSet srs = new SimpleResultSet(this);
srs.addColumn("THE_GEOM", Types.JAVA_OBJECT, "GEOMETRY", 0, 0);
srs.addColumn("ID", Types.INTEGER, 10, 0);
srs.addColumn("ID_COL", Types.INTEGER, 10, 0);
srs.addColumn("ID_ROW", Types.INTEGER, 10, 0);
return srs;
}
}
