Add variable width buffer method to Geometry. (#77)

Author: jericks

doc/api/geom/geometry.rst

@@ -99,6 +99,14 @@ Common Geometry Methods
 
     Construct a geometry that buffers this geometry by the given width.
 
+.. function:: Geometry.variableBuffer
+
+    :arg distances: ``Array`` An array of distances.
+
+    :returns: :class:`geom.Geometry`
+
+    Construct a geometry that buffers this geometry with an array of distances.
+
 .. function:: Geometry.clone
 
     :returns: :class:`geom.Geometry`

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

@@ -34,6 +34,7 @@
 import org.locationtech.jts.geom.Coordinate;
 import org.locationtech.jts.geom.Envelope;
 import org.locationtech.jts.geom.GeometryFactory;
+import org.locationtech.jts.operation.buffer.VariableBuffer;
 import org.locationtech.jts.operation.buffer.BufferOp;
 import org.locationtech.jts.operation.buffer.BufferParameters;
 import org.locationtech.jts.triangulate.VoronoiDiagramBuilder;
@@ -257,6 +258,21 @@ public Geometry buffer(double distance, NativeObject options) {
         return wrapped;
     }
 
+    @JSFunction
+    public Geometry variableBuffer(NativeArray distances) {
+        if (distances.size() == 2) {
+            return (Geometry) GeometryWrapper.wrap(getParentScope(), VariableBuffer.buffer(getGeometry(), getDouble(distances.get(0)), getDouble(distances.get(1))));
+        } else if (distances.size() == 3) {
+            return (Geometry) GeometryWrapper.wrap(getParentScope(), VariableBuffer.buffer(getGeometry(), getDouble(distances.get(0)), getDouble(distances.get(1)), getDouble(distances.get(2))));
+        }  else {
+            return (Geometry) GeometryWrapper.wrap(getParentScope(), VariableBuffer.buffer(getGeometry(), distances.stream().mapToDouble(d -> getDouble(d)).toArray()));
+        }
+    }
+
+    private double getDouble(Object obj) {
+        return ((Number) obj).doubleValue();
+    }
+
     @JSGetter
     public Projection getProjection() {
         return projection;

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

@@ -22,7 +22,7 @@ exports["test: create(point)"] = function() {
 
 exports["test: create(linestring)"] = function() {
     var type = "LineString";
-    var coordinates = [[0, 1], [1, 2]];    
+    var coordinates = [[0, 1], [1, 2]];
     var o, g;
 
     // create a linestring
@@ -196,6 +196,19 @@ exports["test: create non-conforming delaunay triangles"] = function() {
 
 }
 
+exports["test: variable buffer"] = function() {
+
+    var geom = new GEOM.LineString([[1,2], [10,20], [30,50], [100, 150]]);
+    var buffer = geom.variableBuffer([10,50])
+    ASSERT.ok(buffer instanceof GEOM.Polygon)
+
+    buffer = geom.variableBuffer([10, 20, 50])
+    ASSERT.ok(buffer instanceof GEOM.Polygon)
+
+    buffer = geom.variableBuffer([10, 20, 50, 75])
+    ASSERT.ok(buffer instanceof GEOM.Polygon)
+
+}
 
 exports["test: Point"] = require("./geom/test_point");
 exports["test: LineString"] = require("./geom/test_linestring");