5

I'm use JSTS 0.17.0 (https://github.com/bjornharrtell/jsts).
How to split the polygon (polygon to multipolygon or two polygons) ?

enter image description here

Input:

  • POLYGON ((1 1, 1 9, 9 9, 9 1, 1 1))
  • LINESTRING (0.5 5, 9.6 5, 9.6 3.9)

Result (or):

  • MULTIPOLYGON (((9 5, 9 1, 1 1, 1 5, 9 5)),((9 9, 9 5, 1 5, 1 9, 9 9)))
  • GEOMETRYCOLLECTION ( POLYGON ((9 5, 9 1, 1 1, 1 5, 9 5)), POLYGON ((9 9, 9 5, 1 5, 1 9, 9 9)) )

JTS does so:

enter image description here

How do too JSTS ?

PS2
Sorry for my English.

5
  • Do you mean this library github.com/bjornharrtell/jsts?
    – user30184
    Commented Nov 8, 2016 at 7:59
  • Yes, it library.
    – t1nk
    Commented Nov 8, 2016 at 9:07
  • @t1nk do you have any feedback upon my answer?
    – drnextgis
    Commented Nov 21, 2016 at 12:27
  • Where did you get that GUI interface?
    – Donny V.
    Commented Aug 3, 2018 at 13:30
  • I figured it out. Its included with the JTS github code. You have to build the project using maven and then run testbuilder.bat.
    – Donny V.
    Commented Aug 3, 2018 at 15:25

1 Answer 1

4

Something like this:

// Output:
// POLYGON((1 1,1 5,9 5,9 1,1 1))
// POLYGON((1 5,1 9,9 9,9 5,1 5))

var reader = new jsts.io.WKTReader();
var writer = new jsts.io.WKTWriter();

var a = reader.read('POLYGON ((1 1, 1 9, 9 9, 9 1, 1 1))');
var b = reader.read('LINESTRING (0.5 5, 9.6 5, 9.6 3.9)');
var union = a.getExteriorRing().union(b);

var polygonizer = new jsts.operation.polygonize.Polygonizer();
polygonizer.add(union);

var polygons = polygonizer.getPolygons();
for (var i = polygons.iterator(); i.hasNext();) {
    var polygon = i.next();
    console.log(writer.write(polygon));
}
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  • As a result, multipolygon is needed, and it is not valid: self-intersections :( For the separation of polygons - suit
    – t1nk
    Commented Nov 25, 2016 at 7:54
  • In my answer I've got two simple valid polygons. What self-intersection do you mean? Or you have to split not only simple polygons as you pointed in your question?
    – drnextgis
    Commented Nov 25, 2016 at 10:03
  • The result coincides with that obtained in TestBuild, thank you. But I cut multipolygon, and the result will be a multipolygon. The geometry of the cut is perfect - there are no objections, but calculating it fall down because the validity check.
    – t1nk
    Commented Nov 25, 2016 at 13:27

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