Tess simplification

momepy/functional/_elements.py

@@ -15,6 +15,7 @@
 GPD_GE_013 = Version(gpd.__version__) >= Version("0.13.0")
 GPD_GE_10 = Version(gpd.__version__) >= Version("1.0dev")
 LPS_GE_411 = Version(libpysal.__version__) >= Version("4.11.dev")
+SHPLY_GE_250 = Version(shapely.__version__) >= Version("2.5.0dev")
 
 __all__ = [
     "morphological_tessellation",
@@ -128,6 +129,7 @@
     shrink: float = 0.4,
     segment: float = 0.5,
     threshold: float = 0.05,
+    simplify: bool = False,
     n_jobs: int = -1,
 ) -> GeoDataFrame:
     """Generate enclosed tessellation
@@ -175,6 +177,9 @@
         inlude it in the tessellation of that enclosure. Resolves sliver geometry
         issues. If None, the check is skipped and all intersecting buildings are
         considered. By default 0.05
+    simplify: bool, optional
+        Whether to attempt to simplify the resulting tesselation boundaries with
+        ``shapely.coverage_simplify``. By default False.
     n_jobs : int, optional
         The number of jobs to run in parallel. -1 means using all available cores.
         By default -1
@@ -224,6 +229,9 @@
     126  POLYGON ((1603528.593 6464221.033, 1603527.796...                0
     """
 
+    if simplify and not SHPLY_GE_250:
+        raise ImportError("Coverage simplification requires shapely 2.5 or higher.")
+
     if isinstance(geometry.index, MultiIndex):
         raise ValueError(
             "MultiIndex is not supported in `momepy.enclosed_tessellation`."
@@ -265,7 +273,8 @@
 
     # generate tessellation in parallel
     new = Parallel(n_jobs=n_jobs)(
-        delayed(_tess)(*t, threshold, shrink, segment, index_name) for t in tuples
+        delayed(_tess)(*t, threshold, shrink, segment, index_name, simplify)
+        for t in tuples
     )
 
     new_df = pd.concat(new, axis=0)
@@ -297,7 +306,7 @@
     return pd.concat([new_df, singles.drop(columns="position"), clean_blocks])
 
 
-def _tess(ix, poly, blg, threshold, shrink, segment, enclosure_id):
+def _tess(ix, poly, blg, threshold, shrink, segment, enclosure_id, to_simplify):
     """Generate tessellation for a single enclosure. Helper for enclosed_tessellation"""
     # check if threshold is set and filter buildings based on the threshold
     if threshold:
@@ -315,6 +324,11 @@
             return_input=False,
             as_gdf=True,
         )
+        if to_simplify:
+            simpl_collection = shapely.coverage_simplify(
+                tess.geometry, tolerance=1e-1, simplify_boundary=False
+            )
+            tess.geometry = gpd.GeoSeries(simpl_collection.geoms).values
         tess[enclosure_id] = ix
         return tess
 

momepy/functional/tests/test_elements.py

@@ -3,6 +3,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+import shapely
 from geopandas.testing import assert_geodataframe_equal
 from packaging.version import Version
 from pandas.testing import assert_index_equal, assert_series_equal
@@ -13,6 +14,7 @@
 
 GPD_GE_013 = Version(gpd.__version__) >= Version("0.13.0")
 LPS_GE_411 = Version(libpysal.__version__) >= Version("4.11.dev")
+SHPLY_GE_250 = Version(shapely.__version__) >= Version("2.5.0dev")
 
 
 class TestElements:
@@ -330,6 +332,49 @@
         else:
             assert len(blocks.sindex.query_bulk(blocks.geometry, "overlaps")[0]) == 0
 
+    @pytest.mark.skipif(not SHPLY_GE_250, reason="coverage_simplify required")
+    def test_simplified_tesselations(self):
+        n_workers = -1
+        tessellations = mm.enclosed_tessellation(
+            self.df_buildings, self.enclosures.geometry, n_jobs=n_workers
+        )
+        simplified_tessellations = mm.enclosed_tessellation(
+            self.df_buildings, self.enclosures.geometry, simplify=True, n_jobs=n_workers
+        )
+        ## empty enclosures should be unmodified
+        assert_geodataframe_equal(
+            tessellations[tessellations.index < 0],
+            simplified_tessellations[simplified_tessellations.index < 0],
+        )
+        ## simplification should result in less total points
+        orig_points = shapely.get_coordinates(
+            tessellations[tessellations.index >= 0].geometry
+        ).shape
+        simpl_points = shapely.get_coordinates(
+            simplified_tessellations[simplified_tessellations.index >= 0].geometry
+        ).shape
+        assert orig_points > simpl_points
+
+        ## simplification should not modify the external borders of tesselation cells\
+        orig_grouper = tessellations.groupby("enclosure_index")
+        simpl_grouper = simplified_tessellations.groupby("enclosure_index")
+        for idx in np.union1d(
+            tessellations["enclosure_index"].unique(),
+            simplified_tessellations["enclosure_index"].unique(),
+        ):
+            orig_group = orig_grouper.get_group(idx).dissolve().boundary
+            enclosure = self.enclosures.loc[[idx]].dissolve().boundary
+
+            simpl_group = simpl_grouper.get_group(idx).dissolve().boundary
+
+            ## simplified is not different to enclosure
+            ## this needs to be redone
+            assert np.isclose(simpl_group.difference(enclosure).area, 0)
+
+            # simplified is not different to original tess
+            ## this needs to be redone
+            assert np.isclose(simpl_group.difference(orig_group).area, 0)
+
     def test_multi_index(self):
         buildings = self.df_buildings.set_index(["uID", "uID"])
         with pytest.raises(
@@ -375,13 +420,13 @@
         new_blg.loc[22, "geometry"] = new_blg.loc[22, "geometry"].buffer(20)
         new_tess = mm.enclosed_tessellation(new_blg, self.enclosures.geometry, n_jobs=1)
 
-        # assert that buildings 1 and 22 intersect the same enclosure
+        ##assert that buildings 1 and 22 intersect the same enclosure
         inp, res = self.enclosures.sindex.query(
             new_blg.geometry, predicate="intersects"
         )
         assert np.isclose(new_blg.iloc[inp[res == 8]].index.values, [1, 22]).all()
 
-        # assert that there is a tessellation for building 1
+        ### assert that there is a tessellation for building 1
         assert 1 in new_tess.index