Add MultiPolygon support

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## 0.5 - 2018-09-09
+
+### Added
+
+- `MultiPolygon` support
+
 ## 0.4.2 - 2018-08-22
 
 ### Added

centerline/__init__.py

@@ -3,7 +3,7 @@
 from __future__ import unicode_literals
 
 __title__ = 'centerline'
-__version__ = '0.4.2'
+__version__ = '0.5'
 __author__ = 'Filip Todic'
 __license__ = 'MIT'
 __copyright__ = 'Copyright (c) 2014-present Filip Todic'

centerline/io.py

@@ -8,7 +8,7 @@
 from shapely.geometry import mapping, shape
 
 from .main import Centerline
-from .utils import get_ogr_driver, is_polygon
+from .utils import get_ogr_driver, is_valid_geometry
 
 
 def create_centerlines(src, dst, density=0.5):
@@ -50,11 +50,11 @@ def create_centerlines(src, dst, density=0.5):
                     encoding=source.encoding) as destination:
                 for record in source:
                     geom = record.get('geometry')
+                    input_geom = shape(geom)
 
-                    if not is_polygon(geometry_type=geom.get('type')):
+                    if not is_valid_geometry(geometry=input_geom):
                         continue
 
-                    input_geom = shape(geom)
                     attributes = record.get('properties')
                     try:
                         centerline_obj = Centerline(

centerline/main.py

@@ -4,9 +4,11 @@
 
 from numpy import array
 from scipy.spatial import Voronoi
-from shapely.geometry import LineString, MultiLineString, Polygon
+from shapely.geometry import LineString, MultiLineString, MultiPolygon
 from shapely.ops import unary_union
 
+from .utils import is_valid_geometry
+
 
 class Centerline(MultiLineString):
     """
@@ -40,9 +42,10 @@ def __init__(self, input_geom, interpolation_dist=0.5, **attributes):
             ValueError: invalid input geometry
 
         """
-        if not isinstance(input_geom, Polygon):
+        if not is_valid_geometry(input_geom):
             raise ValueError(
-                'Input geometry must be of type shapely.geometry.Polygon!'
+                'Input geometry must be of type shapely.geometry.Polygon '
+                'or shapely.geometry.MultiPolygon!'
             )
 
         self._input_geom = input_geom
@@ -112,17 +115,24 @@ def __densify_border(self):
             [[X1, Y1], [X2, Y2], ..., [Xn, Yn]
 
         """
-        if len(self._input_geom.interiors) == 0:
-            exterIN = LineString(self._input_geom.exterior)
-            points = self.__fixed_interpolation(exterIN)
-
+        if isinstance(self._input_geom, MultiPolygon):
+            polygons = [polygon for polygon in self._input_geom]
         else:
-            exterIN = LineString(self._input_geom.exterior)
-            points = self.__fixed_interpolation(exterIN)
+            polygons = [self._input_geom]
+
+        points = []
+        for polygon in polygons:
+            if len(polygon.interiors) == 0:
+                exterior = LineString(polygon.exterior)
+                points += self.__fixed_interpolation(exterior)
+
+            else:
+                exterior = LineString(polygon.exterior)
+                points += self.__fixed_interpolation(exterior)
 
-            for j in range(len(self._input_geom.interiors)):
-                interIN = LineString(self._input_geom.interiors[j])
-                points += self.__fixed_interpolation(interIN)
+                for j in range(len(polygon.interiors)):
+                    interior = LineString(polygon.interiors[j])
+                    points += self.__fixed_interpolation(interior)
 
         return points
 

centerline/utils.py

@@ -5,26 +5,27 @@
 import os
 
 from osgeo import gdal, ogr
+from shapely.geometry import MultiPolygon, Polygon
 
 # Enable GDAL/OGR exceptions
 gdal.UseExceptions()
 
 
-ALLOWED_INPUT_GEOMETRY = 'Polygon'
+ALLOWED_INPUT_GEOMETRIES = ('Polygon', 'MultiPolygon')
 
 
-def is_polygon(geometry_type):
+def is_valid_geometry(geometry):
     """
-    Confirm that the geometry type is of type Polygon.
+    Confirm that the geometry type is of type Polygon or MultiPolygon.
 
     Args:
-        geometry_type (str): geometry type
+        geometry (BaseGeometry): BaseGeometry instance (e.g. Polygon)
 
     Returns:
         bool
 
     """
-    if geometry_type == ALLOWED_INPUT_GEOMETRY:
+    if isinstance(geometry, Polygon) or isinstance(geometry, MultiPolygon):
         return True
     else:
         return False

tests/test_main.py

@@ -14,7 +14,7 @@
 
 class TestCenterlineSupportedGeometryTypes(TestCase):
     """
-    Only Polygons should be supported.
+    Only Polygons and MultiPolygons should be supported.
 
     For more information about creating the geometry objects (like the
     ones used below) see The Shapely User Manual:
@@ -39,11 +39,14 @@ def test__polygon_with_interior_ring__returns_multilinestring(self):
         self.assertIsInstance(centerline, MultiLineString)
 
     def test__multipolygon__raises_valueerror(self):
-        POLYGONS = [Point(i, 0).buffer(0.1) for i in range(2)]
-        MULTIPOLYGON = MultiPolygon(POLYGONS)
+        POLYGON_1 = Polygon([[0, 0], [0, 4], [4, 4], [4, 0]])
+        POLYGON_2 = Polygon([[5, 5], [5, 9], [9, 9], [9, 5]])
 
-        with self.assertRaises(ValueError):
-            Centerline(MULTIPOLYGON)
+        MULTIPOLYGON = MultiPolygon([POLYGON_1, POLYGON_2])
+
+        centerline = Centerline(MULTIPOLYGON)
+
+        self.assertIsInstance(centerline, MultiLineString)
 
     def test__point__raises_valueerror(self):
         POINT = Point(0, 0)

tests/test_utils.py

@@ -5,20 +5,37 @@
 import os
 from unittest import TestCase
 
-from centerline.utils import get_ogr_driver, is_polygon
+from shapely import geometry
+
+from centerline.utils import get_ogr_driver, is_valid_geometry
 
 TESTS_DIR = os.path.dirname(os.path.abspath(__file__))
 SHP_DIR = os.path.join(TESTS_DIR, 'data', 'shp')
 GEOJSON_DIR = os.path.join(TESTS_DIR, 'data', 'geojson')
 
 
-class TestIsPolygon(TestCase):
+class TestIsValidGeometry(TestCase):
+
+    def test_point_returns_false(self):
+        self.assertFalse(is_valid_geometry(geometry.Point()))
+
+    def test_multipoint_returns_false(self):
+        self.assertFalse(is_valid_geometry(geometry.MultiPoint()))
+
+    def test_linestring_returns_false(self):
+        self.assertFalse(is_valid_geometry(geometry.LineString()))
+
+    def test_multilinestring_returns_false(self):
+        self.assertFalse(is_valid_geometry(geometry.MultiLineString()))
+
+    def test_linearring_returns_false(self):
+        self.assertFalse(is_valid_geometry(geometry.LinearRing()))
 
-    def test__returns_true(self):
-        self.assertTrue(is_polygon('Polygon'))
+    def test_polygon_returns_true(self):
+        self.assertTrue(is_valid_geometry(geometry.Polygon()))
 
-    def test__returns_false_for_multipolygon(self):
-        self.assertFalse(is_polygon('MultiPolygon'))
+    def test_multipolygon_returns_true(self):
+        self.assertTrue(is_valid_geometry(geometry.MultiPolygon()))
 
 
 class TestGetOgrDriver(TestCase):