Add voronoi diagram method to Geometry (#68)

Author: jericks

examples/geometry/delaunayTriangle.js

@@ -0,0 +1,7 @@
+var geom = require('geoscript/geom');
+var viewer = require('geoscript/viewer');
+
+var polygon = geom.Point([1,1]).buffer(50);
+var points = polygon.randomPoints(100);
+var triangles = points.createDelaunayTriangles(true);
+viewer.draw(triangles);

examples/geometry/voronoiDigram.js

@@ -0,0 +1,7 @@
+var geom = require('geoscript/geom');
+var viewer = require('geoscript/viewer');
+
+var polygon = geom.Point([1,1]).buffer(50);
+var points = polygon.randomPoints(20);
+var diagram = points.createVoronoiDiagram();
+viewer.draw(diagram);

src/main/java/org/geoscript/js/geom/Geometry.java

@@ -35,6 +35,7 @@
 import org.locationtech.jts.geom.GeometryFactory;
 import org.locationtech.jts.operation.buffer.BufferOp;
 import org.locationtech.jts.operation.buffer.BufferParameters;
+import org.locationtech.jts.triangulate.VoronoiDiagramBuilder;
 import org.locationtech.jts.simplify.DouglasPeuckerSimplifier;
 
 public class Geometry extends GeoObject implements Wrapper {
@@ -303,6 +304,15 @@ public ScriptableObject densify(double tolerance) {
         return densified;
     }
 
+    @JSFunction
+    public ScriptableObject createVoronoiDiagram() {
+        VoronoiDiagramBuilder builder = new VoronoiDiagramBuilder();
+        builder.setSites(geometry);
+        ScriptableObject voronoiDiagram = GeometryWrapper.wrap(getParentScope(), builder.getDiagram(Geometry.factory));
+        ((Geometry) voronoiDiagram).projection = projection;
+        return voronoiDiagram;
+    }
+
     @JSFunction
     public ScriptableObject randomPoints(int number) {
         org.locationtech.jts.shape.random.RandomPointsBuilder builder = new org.locationtech.jts.shape.random.RandomPointsBuilder(factory);

src/test/resources/org/geoscript/js/tests/geoscript/test_geom.js

@@ -157,6 +157,16 @@ exports["test: create(bounds)"] = function() {
 
 };
 
+exports["test: create voronoi diagram"] = function() {
+
+    var geom = GEOM.Point([1,1]).buffer(50)
+    var points = geom.randomPoints(20)
+    var diagram = points.createVoronoiDiagram()
+    ASSERT.ok(diagram instanceof GEOM.GeometryCollection)
+    ASSERT.ok(diagram.components.length > 0, "there should be more than 0 polygons");
+
+}
+
 exports["test: create random points"] = function() {
 
     var geom = GEOM.Point([1,1]).buffer(10)