Hi folks,
here is my working solution,adapted to my requirements:
private String jtsSplit(Polygon p, LineString l) {
/*
* Use MCIndexNoder to node
the polygon and linestring together, Polygonizer to polygonize the
noded edges, and then PointLocater to determine which of the
resultant
polygons correspond to the input polygon. */
StringBuffer _buffer = new StringBuffer();
IntersectionAdder _intersector=new IntersectionAdder(new
RobustLineIntersector());
MCIndexNoder _mci = new MCIndexNoder();
_mci.setSegmentIntersector(_intersector);
NodedSegmentString _pseg = new
NodedSegmentString(p.getCoordinates(), null);
NodedSegmentString _lseg = new
NodedSegmentString(l.getCoordinates(), null);
Vector<NodedSegmentString> _v = new Vector<NodedSegmentString>();
_v.add(_pseg);
_v.add(_lseg);
_mci.computeNodes(_v);
GeometryFactory _fac = new GeometryFactory();
Polygonizer _polygonizer = new Polygonizer();
Vector<LineString> _ls = new Vector<LineString>();
for (Object o : _mci.getMonotoneChains()) {
MonotoneChain _mtc = (MonotoneChain) o;
LineString _line = _fac.createLineString(_mtc.getCoordinates());
_ls.add(_line);
}
Geometry nodedLineStrings = _ls.get(0);
for (int i = 1; i < _ls.size(); i++) {
nodedLineStrings = nodedLineStrings.union(_ls.get(i));
}
_polygonizer.add(nodedLineStrings);
Collection<Polygon> _polygons = _polygonizer.getPolygons();
PointLocator _pl=new PointLocator();
for (Polygon _p : _polygons) {
if
(_pl.locate(_p.getInteriorPoint().getCoordinate(),p)==Location.INTERIOR)
{
_buffer.append("<polygon>");
_buffer.append(_p);
_buffer.append("</polygon>");
}
}
return (_buffer.toString());
}
Michael Michaud schrieb:
Sorry, I used some jump code,
pure jts could be :
import com.vividsolutions.jts.noding.*;
import com.vividsolutions.jts.algorithm.RobustLineIntersector;
gf = new GeometryFactory();
// add the linestrings to a list of NodedSegmentString;
List list = new ArrayList();
list.add(new NodedSegmentString(geometry1.getCoordinates(), null));
list.add(new NodedSegmentString(geometry2.getCoordinates(), null));
// create a noder and computes the nodes
Noder noder = new MCIndexNoder();
noder.setSegmentIntersector(new IntersectionAdder(new
RobustLineIntersector()));
noder.computeNodes(list);
// get noded substrings and create LINESTRING geometries from them
list = noder.getNodedSubstrings();
for (Object substring : list)
print(gf.createLineString(((NodedSegmentString)substring).getCoordinates()));
// you still have to polygonize your noded linestrings
Hope that helps
Michaël
Dipl. Inf. Carsten Eider a écrit :
Hi list,
i am getting sick while trying to resolve my problem of splitting a
polygon(assumd to have no wholes within),
it is driving me crazy! martin gave the hint:
"Use MCIndexNoder to node the polygon and linestring together,
Polygonizer to polygonize the noded edges, and then PointLocater to
determine which of the resultant polygons correspond to the input
polygon. "
Here is my non working attempt
Polygon p, LineString l;
//Use MCIndexNoder
//Setup intersector any classes implementing SegmentIntersector
(InteriorIntersectionFinder
<mailbox:///G%7C/Documents%20and%20Settings/Travail/Application%20Data/Thunderbird/Profiles/nwn2wsnb.default/Mail/Local%20Folders/Inbox?number=171338383&header=quotebody&part=1.1.1.2&filename=InteriorIntersectionFinder.html>,
IntersectionAdder
<mailbox:///G%7C/Documents%20and%20Settings/Travail/Application%20Data/Thunderbird/Profiles/nwn2wsnb.default/Mail/Local%20Folders/Inbox?number=171338383&header=quotebody&part=1.1.1.3&filename=IntersectionAdder.html>,
IntersectionFinderAdder
<mailbox:///G%7C/Documents%20and%20Settings/Travail/Application%20Data/Thunderbird/Profiles/nwn2wsnb.default/Mail/Local%20Folders/Inbox?number=171338383&header=quotebody&part=1.1.1.4&filename=IntersectionFinderAdder.html>,
LineIntersectionAdder
<mailbox:///G%7C/Documents%20and%20Settings/Travail/Application%20Data/Thunderbird/Profiles/nwn2wsnb.default/Mail/Local%20Folders/Inbox?number=171338383&header=quotebody&part=1.1.1.5&filename=LineIntersectionAdder.html>,
SegmentIntersectionDetector
<mailbox:///G%7C/Documents%20and%20Settings/Travail/Application%20Data/Thunderbird/Profiles/nwn2wsnb.default/Mail/Local%20Folders/Inbox?number=171338383&header=quotebody&part=1.1.1.6&filename=SegmentIntersectionDetector.html>)
have been tested!
SegmentIntersectionDetector _intersector = new
SegmentIntersectionDetector(new RobustLineIntersector());
_intersector.setFindProper(true);
_intersector.setFindAllIntersectionTypes(true);
//Wouldn't it be better to setup intersector within the constructor?
MCIndexNoder _mci = new MCIndexNoder();
_mci.setSegmentIntersector(_intersector);
// Add my polygon and my LineString
NodedSegmentString _pseg = new
NodedSegmentString(p.getCoordinates(), null);
NodedSegmentString _lseg = new
NodedSegmentString(l.getCoordinates(), null);
Vector<NodedSegmentString> _v = new Vector<NodedSegmentString>();
//order of adding doesn't alter result
_v.add(_pseg);
_v.add(_lseg);
//lets compute the nodes, whatever this does mean!
_mci.computeNodes(_v);
//here is my polygonizer
Polygonizer _polygonizer = new Polygonizer();
//let's add thsi monotonechains, whatever they mean!
for (Object o : _mci.getMonotoneChains()) {
MonotoneChain _mtc = (MonotoneChain) o;
//Convert chain to a linestring, is thsi correct?
LineString _line =
_fac.createLineString(_mtc.getCoordinates());
System.out.println(_line);
_polygonizer.add(_line);
}
//Here are my hopefully correct poylgons!
Collection<Polygon> _polygons = _polygonizer.getPolygons();
for (Polygon _p : _polygons) {
/System.out.println(_p);
}
Example 1:
l=LINESTRING (0 0,4 5, 5 4,10 10);
p=POLYGON(0 0,10 0,10 10 ,0 10, 3 8,0 0)
pgsql:<polygon>POLYGON ((10 10, 10 0, 0 0, 4 5, 5 4, 10
10))</polygon><polygon>POLYGON ((0 0, 3 8, 0 10, 10 10, 5 4, 4 5, 0
0))</polygon>
jts:<polygon>POLYGON ((5 4, 4 5, 0 0, 3 8, 0 10, 10 10, 5
4))</polygon><polygon>POLYGON ((0 0, 4 5, 5 4, 10 10, 10 0, 0
0))</polygon>
jts==pgsql==>Correct GREAT
Example 2:
l=LINESTRING (-1 -1,4 5, 5 4,11 11);
p=POLYGON(0 0,10 0,10 10 ,0 10, 3 8,0 0)
pgsql:<polygon>POLYGON ((10 9.83333333333333, 10 0, 0 0,
0.136363636363636 0.363636363636364, 4 5, 5 4, 10
9.83333333333333))</polygon><polygon>POLYGON ((0.136363636363636
0.363636363636364, 3 8, 0 10, 10 10, 10 9.83333333333333, 5 4, 4 5,
0.136363636363636 0.363636363636364))</polygon>
jts:<polygon>POLYGON ((0 0, 3 8, 0 10, 10 10, 10 0, 0 0))</polygon>
jts!=pgsql, damn where is my second polygon as expected? why do i
get just my original polygon?
Example 3
l=LINESTRING (0 0,4 5, 5 4,10 10,10 6,0 6)
p=POLYGON(0 0,10 0,10 10 ,0 10, 3 8,0 0)
pgsql:<polygon>POLYGON ((10 6, 10 0, 0 0, 4 5, 5 4, 6.66666666666667
6, 10 6))</polygon><polygon>POLYGON ((10 10, 10 6, 6.66666666666667
6, 10 10))</polygon><polygon>POLYGON ((2.25 6, 3 8, 0 10, 10 10,
6.66666666666667 6, 2.25 6))</polygon><polygon>POLYGON ((0 0, 2.25
6, 6.66666666666667 6, 5 4, 4 5, 0 0))</polygon>
jts:<polygon>POLYGON ((5 4, 4 5, 0 0, 3 8, 0 10, 10 10, 5
4))</polygon><polygon>POLYGON ((0 0, 4 5, 5 4, 10 10, 10 0, 0
0))</polygon>
jts!=pgsql, why the hell are there only two polygons left? where are
the other two as expected?
Any suggestions are very appreciated!
Maybe i should offer a reward of a box of good german beer !
TIA Carsten
--
Mit freundlichen Grüßen / Yours faithfully
Carsten Eider
Dipl. Inf. (FH)
Kompetenzzentrum für Innovative Informationssysteme
c/o Fachhochschhule Bingen / University of applied sciences Bingen
Berlinstraße 109
55411 Bingen
Tel: +49 (0) 6721 / 409-179
Fax: +49 (0) 6721 / 409-158
email: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
Internet: iis.fh-bingen.de
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--
Mit freundlichen Grüßen / Yours faithfully
Carsten Eider
Dipl. Inf. (FH)
Kompetenzzentrum für Innovative Informationssysteme
c/o Fachhochschhule Bingen / University of applied sciences Bingen
Berlinstraße 109
55411 Bingen
Tel: +49 (0) 6721 / 409-179
Fax: +49 (0) 6721 / 409-158
email: [EMAIL PROTECTED]
Internet: iis.fh-bingen.de
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