If there is any method or class who can do the job. So, I want to know if I
don't miss something.
__-
-Original Message-
From: jts-devel-boun...@lists.jump-project.org
[mailto:jts-devel-boun...@lists.jump-project.org] On Behalf Of Martin Davis
Sent: donderdag 5 november 2009 17:54
To: JTS Topology Suite Development
Subject: Re: [jts-devel] Extend a LineString in a Polygon
Minze,
What do you mean by "still curious about the API support"?
Tolsma, Minze wrote:
> This Works fine for me. I'm still curious about the API support. :-)
>
> Thanks!
>
> Minze
>
> -Original Message-
> From: jts-devel-boun...@lists.jump-project.org
> [mailto:jts-devel-boun...@lists.jump-project.org] On Behalf Of Michael Bedward
> Sent: donderdag 5 november 2009 1:56
> To: JTS Topology Suite Development
> Subject: Re: [jts-devel] Extend a LineString in a Polygon
>
> Below is one way of doing it. I can almost guarantee there will be a
> much better way :)
>
> Michael
>
>
> import com.vividsolutions.jts.geom.Coordinate;
> import com.vividsolutions.jts.geom.Geometry;
> import com.vividsolutions.jts.geom.GeometryFactory;
> import com.vividsolutions.jts.geom.LineString;
> import com.vividsolutions.jts.geom.Point;
> import com.vividsolutions.jts.io.WKTReader;
>
> public class Foo {
>
> public static void main(String[] args) throws Exception {
> GeometryFactory gf = new GeometryFactory();
>
> WKTReader reader = new WKTReader(gf);
>
> Geometry poly = reader.read("POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))");
> // a line inside the square
> LineString line = (LineString) reader.read("LINESTRING(4 4, 6 5)");
>
> if (!line.intersects(poly)) {
> System.out.println("line does not intersect polygon");
> return;
> }
>
> Coordinate[] coords = line.getCoordinates();
> final int END = coords.length - 1;
>
> // extend start point beyond poly
> Coordinate newStart = new Coordinate(coords[0]);
> Point testP = gf.createPoint(newStart);
> while (poly.contains(testP)) {
> newStart.x += newStart.x - coords[1].x;
> newStart.y += newStart.y - coords[1].y;
> testP = gf.createPoint(newStart);
> }
>
> // extend end point beyond poly
> Coordinate newEnd = new Coordinate(coords[END]);
> testP = gf.createPoint(newEnd);
> while (poly.contains(testP)) {
> newEnd.x += newEnd.x - coords[END-1].x;
> newEnd.y += newEnd.y - coords[END-1].y;
> testP = gf.createPoint(newEnd);
> }
>
> LineString extended = gf.createLineString(new
> Coordinate[]{newStart, newEnd});
> System.out.println("extended line: " + extended);
> System.out.println("crosses polygon: " + extended.crosses(poly));
> }
>
> }
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>
>
>
>
>
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>
--
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022
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