Re: [Geotools-gt2-users] intersection MultiLineString-Polygon = MultiLineString

[Michael B. <mic...@gm...>]

Hi Jo

I think you want to do multiLineString.intersection( polygon ).  This
will give you a multi line string made up of lines within the polygon.
 If the lines cross within the polygon they will be cut at the
crossing points.

Here's a demo

        GeometryFactory gf = new GeometryFactory();

        // polygon outer ring
        Coordinate[] outerCoords = {
            new Coordinate(0,0),
            new Coordinate(0,10),
            new Coordinate(10,10),
            new Coordinate(10,0),
            new Coordinate(0,0)
        };

        LinearRing outerRing = gf.createLinearRing(outerCoords);
        LinearRing[] holes = null;

        Polygon poly = gf.createPolygon(outerRing, holes);

        Coordinate[] line1Coords = {
            new Coordinate(-100,2), new Coordinate(100,2)
        };

        Coordinate[] line2Coords = {
            new Coordinate(-100,7), new Coordinate(100,7)
        };

        Coordinate[] line3Coords = {
            new Coordinate(5, 100), new Coordinate(5, -100)
        };

        LineString[] lines = {
            gf.createLineString(line1Coords),
            gf.createLineString(line2Coords),
            gf.createLineString(line3Coords)
        };

        MultiLineString mls = gf.createMultiLineString(lines);

        MultiLineString within = (MultiLineString) mls.intersection(poly);

        for (int i = 0; i < within.getNumGeometries(); i++) {
            LineString line = (LineString) within.getGeometryN(i);
            System.out.println("line " + i +
                    "(" + line.getStartPoint() + ") (" +
line.getEndPoint() + ")");
        }


Hope this helps

Michael

2008/10/15 Jo <new...@pu...>:
>
> Hello,
>
> I want to intersect a MultiLineString with a polygon. This operation should
> return a cropped
> MultiLineString.
> polygon.intersection(MultiLineString) returns a Geometry which I can't cast
> to the subclass
> MultiLineString.
> How can I convert the returned Geometry to a MultiLineString? Or is there
> another way
> how to make this intersection and get a cropped MultiLineString back.
>
> Thanks,
>
> Jo
>
> --
> View this message in context: http://n2.nabble.com/intersection-MultiLineString-Polygon-%3D-MultiLineString-tp1336428p1336428.html
> Sent from the geotools-gt2-users mailing list archive at Nabble.com.
>
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