/*
* This is part of Geomajas, a GIS framework, http://www.geomajas.org/.
*
* Copyright 2008-2011 Geosparc nv, http://www.geosparc.com/, Belgium.
*
* The program is available in open source according to the GNU Affero
* General Public License. All contributions in this program are covered
* by the Geomajas Contributors License Agreement. For full licensing
* details, see LICENSE.txt in the project root.
*/
package org.geomajas.gwt.client.spatial.snapping;
import java.util.ArrayList;
import java.util.List;
import org.geomajas.geometry.Coordinate;
import org.geomajas.gwt.client.spatial.LineSegment;
import org.geomajas.gwt.client.spatial.geometry.Geometry;
/**
* <p>
* Snapping algorithm that not only snaps to end-points of nearby geometries, but to any point on any of the edges as
* well. As you might guess, this is a heavier calculation then the {@link ClosestPointAlgorithm}. It tries to calculate
* distances between the given coordinate, and any of the edges (one-by-one) and decides on the shortest.
* </p>
*
* @author Pieter De Graef
*/
public class NearestAlgorithm extends SnappingAlgorithm {
/**
* The maximum snapping distance, as defined in a snapping rules.
*/
private double ruleDistance;
/**
* A list of coordinate arrays. It contains coordinate arrays from either LineStrings or LinearRings or point. The
* point is that only between coordinates in the same array can edges exist.
*/
private List<Coordinate[]> coordinates;
//-------------------------------------------------------------------------
// Constructor:
//-------------------------------------------------------------------------
public NearestAlgorithm(List<Geometry> geometries, double ruleDistance) {
super(geometries);
this.ruleDistance = ruleDistance;
coordinates = getCoordinateArrays(geometries);
}
//-------------------------------------------------------------------------
// SnappingAlgorithm implementation:
//-------------------------------------------------------------------------
/**
* Calculates a snapping point from the given coordinate.
*
* @param original
* The original and unsnapped coordinate.
* @param threshold
* A threshold value that needs to be beaten in order to snap. Only if the distance between the original
* and the candidate coordinate is smaller then this threshold, can the candidate coordinate be a snapped
* coordinate.
* @return Returns the eventual snapped coordinate, or null if no snapping occurred.
*/
Coordinate getSnappingPoint(Coordinate original, double threshold) {
minimumDistance = Double.MAX_VALUE;
Coordinate snappingPoint = null;
double currThreshold = threshold;
for (Coordinate[] coordinateArray : coordinates) {
for (int j = 1; j < coordinateArray.length; j++) {
LineSegment line = new LineSegment(coordinateArray[j], coordinateArray[j - 1]);
double distance = line.distance(original);
if (distance < currThreshold && distance < ruleDistance) {
currThreshold = distance;
minimumDistance = distance;
snappingPoint = line.nearest(original);
}
}
}
return snappingPoint;
}
// -------------------------------------------------------------------------
// Private methods:
// -------------------------------------------------------------------------
/**
* Transform the list of geometries into a list of coordinate arrays.
*/
private List<Coordinate[]> getCoordinateArrays(List<Geometry> geometries) {
List<Coordinate[]> res = new ArrayList<Coordinate[]>();
for (Geometry geometry : geometries) {
res.add(geometry.getCoordinates());
}
return res;
}
}