| gvSIG desktop 1

package org.gvsig.jts;

import com.vividsolutions.jts.algorithms.SnapCGAlgorithms;

import com.vividsolutions.jts.geom.Coordinate;

import com.vividsolutions.jts.geom.CoordinateList;

import com.vividsolutions.jts.geom.Geometry;

import com.vividsolutions.jts.geom.GeometryFactory;

import com.vividsolutions.jts.geom.LineSegment;

import com.vividsolutions.jts.geom.LineString;

/**

 * Cracks the geometries of a topology's layers to force the sharing of

 * coordinates

 * 

 */

public class GeometryCracker {

        private static GeometryFactory geomFactory = new GeometryFactory();

        private LineSegment seg = new LineSegment(); 

        private double snapTolerance;

        public GeometryCracker(double snapTolerance)

        {

                this.snapTolerance = snapTolerance;

        }

        /**

         * "Cracks" a geometry a with the points of a given geometry b.

         * @param a

         * @param b

         * @param snapTolerance

         * @return

         */

        public static Geometry crack(LineString a, LineString b, double snapTolerance) {

                GeometryCracker cracker = new GeometryCracker(snapTolerance);

                Coordinate[] newCoordsA = cracker.crackTo(a.getCoordinates(), b.getCoordinates());

                return geomFactory.createLinearRing(newCoordsA);

        }

        /*

         * This code is extracted from the class LineStringSnapper of JTS 

         * */

        private Coordinate[] crackTo(Coordinate[] srcPts, Coordinate[] snapPts) {

                CoordinateList coordList = new CoordinateList(srcPts);

                crackSegments(coordList, snapPts);

                Coordinate[] newPts = coordList.toCoordinateArray();

                return newPts;

        }

        private void crackSegments(CoordinateList srcCoords, Coordinate[] snapPts) {

                int distinctPtCount = snapPts.length;

                Coordinate firstPoint = snapPts[0];

                Coordinate lastPoint = snapPts[snapPts.length - 1];

                if(SnapCGAlgorithms.snapEquals2D(firstPoint, lastPoint, snapTolerance))

                        distinctPtCount = snapPts.length - 1;

                for (int i = 0; i < distinctPtCount; i++) {

                        Coordinate snapPt = snapPts[i];

                        int index = findSegmentIndexToSnap(snapPt, srcCoords);

                        if (index >= 0) {

                                srcCoords.add(index + 1, new Coordinate(snapPt), false);

                        }

                }

        }

        private int findSegmentIndexToSnap(Coordinate snapPt, CoordinateList srcCoords) {

                double minDist = Double.MAX_VALUE;

                int snapIndex = -1;

                for (int i = 0; i < srcCoords.size() - 1; i++) {

                        seg.p0 = (Coordinate) srcCoords.get(i);

                        seg.p1 = (Coordinate) srcCoords.get(i + 1);

                        if(SnapCGAlgorithms.snapEquals2D(seg.p0, snapPt, snapTolerance) 

                                        || SnapCGAlgorithms.snapEquals2D(seg.p1, snapPt, snapTolerance))

                                return -1;

                        double dist = seg.distance(snapPt);

                        if (dist < snapTolerance && dist < minDist) {

                                minDist = dist;

                                snapIndex = i;

                        }

                }

                return snapIndex;

        }

}