Merge pull request #64 from geoscript/GEOSCRIPTPY-61.VariableBuffer

Add variable width buffer

Author: jericks

geoscript/geom/__init__.py

@@ -11,7 +11,7 @@
 from compoundring import CompoundRing
 from bounds import Bounds
 from geom import Geometry
-from geom import prepare, simplify, densify, transform, buffer, delaunay, voronoi, randomPoints, createSierpinskiCarpet
+from geom import prepare, simplify, densify, transform, buffer, delaunay, voronoi, randomPoints, createSierpinskiCarpet, variableBuffer
 from io.wkt import readWKT, writeWKT, fromWKT
 from io.wkb import readWKB, writeWKB, fromWKB, toWKB
 from io.json import writeJSON, readJSON

geoscript/geom/geom.py

@@ -16,6 +16,7 @@
 from org.geotools.referencing.operation.transform import AffineTransform2D
 from org.locationtech.jts.shape.random import RandomPointsBuilder
 from org.locationtech.jts.shape.fractal import SierpinskiCarpetBuilder
+from org.locationtech.jts.operation.buffer import VariableBuffer
 from geoscript.geom.bounds import Bounds
 
 _factory = GeometryFactory()
@@ -155,6 +156,21 @@ def buffer(g, distance, singleSided=False):
 
   return BufferOp.bufferOp(g, distance, bp) 
 
+def variableBuffer(g, distances):
+  """
+  Computes a buffer with variable distances.
+
+  *g* is the :class:`Geometry <geoscript.geom.Geometry>` to buffer.
+
+  *distances* is an array of buffer distances
+  """
+  if len(distances) == 2:
+    return VariableBuffer.buffer(g, distances[0], distances[1])
+  elif len(distances) == 3:
+    return VariableBuffer.buffer(g, distances[0], distances[1], distances[2])
+  else:
+    return VariableBuffer.buffer(g, distances)
+
 def randomPoints(g, number):
   """
   Create a number of random Points within the given Geometry

tests/test_geom.py

@@ -236,3 +236,14 @@ def testCreateSierpinskiCarpet(self):
     bounds = geom.Bounds(-180,-90,180,90)
     sierpinskiCarpet = geom.createSierpinskiCarpet(bounds, 50)
     assert sierpinskiCarpet.getNumGeometries() > 0
+
+  def testVariableBuffer(self):
+    line = geom.LineString((1,2), (10,20), (30,50), (100, 150))
+    buffer = geom.variableBuffer(line, [10,50])
+    assert str(buffer).startswith("POLYGON")
+
+    buffer = geom.variableBuffer(line, [10, 20, 50])
+    assert str(buffer).startswith("POLYGON")
+
+    buffer = geom.variableBuffer(line, [10, 20, 50, 75])
+    assert str(buffer).startswith("POLYGON")