Another self-intersection corner case handling

sahi/models/detectron2.py

@@ -149,9 +149,9 @@ def _create_object_prediction_list_from_original_predictions(
             object_prediction_list = [
                 ObjectPrediction(
                     bbox=box.tolist() if mask is None else None,
-                    segmentation=get_coco_segmentation_from_bool_mask(mask.detach().cpu().numpy())
-                    if mask is not None
-                    else None,
+                    segmentation=(
+                        get_coco_segmentation_from_bool_mask(mask.detach().cpu().numpy()) if mask is not None else None
+                    ),
                     category_id=category_id.item(),
                     category_name=self.category_mapping[str(category_id.item())],
                     shift_amount=shift_amount,

sahi/utils/coco.py

@@ -224,28 +224,7 @@ def __init__(
         self._shapely_annotation = shapely_annotation
 
     def get_sliced_coco_annotation(self, slice_bbox: List[int]):
-        def filter_polygons(geometry):
-            """
-            Filters out and returns only Polygon or MultiPolygon components of a geometry.
-            If geometry is a Polygon, it converts it into a MultiPolygon.
-            If it's a GeometryCollection, it filters to create a MultiPolygon from any Polygons in the collection.
-            Returns an empty MultiPolygon if no Polygon or MultiPolygon components are found.
-            """
-            if isinstance(geometry, Polygon):
-                return MultiPolygon([geometry])
-            elif isinstance(geometry, MultiPolygon):
-                return geometry
-            elif isinstance(geometry, GeometryCollection):
-                polygons = [geom for geom in geometry.geoms if isinstance(geom, Polygon)]
-                return MultiPolygon(polygons) if polygons else MultiPolygon()
-            return MultiPolygon()
-
         shapely_polygon = box(slice_bbox[0], slice_bbox[1], slice_bbox[2], slice_bbox[3])
-        samp = self._shapely_annotation.multipolygon
-        if not samp.is_valid:
-            valid = make_valid(samp)
-            valid = filter_polygons(valid)
-            self._shapely_annotation.multipolygon = valid
         intersection_shapely_annotation = self._shapely_annotation.get_intersection(shapely_polygon)
         return CocoAnnotation.from_shapely_annotation(
             intersection_shapely_annotation,

sahi/utils/shapely.py

@@ -3,7 +3,8 @@
 
 from typing import List
 
-from shapely.geometry import CAP_STYLE, JOIN_STYLE, MultiPolygon, Polygon, box
+from shapely.geometry import CAP_STYLE, JOIN_STYLE, GeometryCollection, MultiPolygon, Polygon, box
+from shapely.validation import make_valid
 
 
 def get_shapely_box(x: int, y: int, width: int, height: int) -> Polygon:
@@ -21,15 +22,36 @@ def get_shapely_box(x: int, y: int, width: int, height: int) -> Polygon:
 
 def get_shapely_multipolygon(coco_segmentation: List[List]) -> MultiPolygon:
     """
-    Accepts coco style polygon coords and converts it to shapely multipolygon object
+    Accepts coco style polygon coords and converts it to valid shapely multipolygon object
     """
+
+    def filter_polygons(geometry):
+        """
+        Filters out and returns only Polygon or MultiPolygon components of a geometry.
+        If geometry is a Polygon, it converts it into a MultiPolygon.
+        If it's a GeometryCollection, it filters
+        to create a MultiPolygon from any Polygons in the collection.
+        Returns an empty MultiPolygon if no Polygon or MultiPolygon components are found.
+        """
+        if isinstance(geometry, Polygon):
+            return MultiPolygon([geometry])
+        elif isinstance(geometry, MultiPolygon):
+            return geometry
+        elif isinstance(geometry, GeometryCollection):
+            polygons = [geom for geom in geometry.geoms if isinstance(geom, Polygon)]
+            return MultiPolygon(polygons) if polygons else MultiPolygon()
+        return MultiPolygon()
+
     polygon_list = []
     for coco_polygon in coco_segmentation:
         point_list = list(zip(coco_polygon[0::2], coco_polygon[1::2]))
         shapely_polygon = Polygon(point_list)
         polygon_list.append(shapely_polygon)
     shapely_multipolygon = MultiPolygon(polygon_list)
 
+    if not shapely_multipolygon.is_valid:
+        shapely_multipolygon = filter_polygons(make_valid(shapely_multipolygon))
+
     return shapely_multipolygon
 
 

tests/test_shapelyutils.py

@@ -26,6 +26,12 @@ def test_get_shapely_multipolygon(self):
         self.assertEqual(shapely_multipolygon.area, 41177.5)
         self.assertTupleEqual(shapely_multipolygon.bounds, (1, 1, 325, 200))
 
+    def test_get_shapely_multipolygon_naughty(self):
+        # self-intersection case
+        coco_segmentation = [[3559.0, 2046.86, 3.49, 2060.0, 3540.9, 3249.7, 2060.0, 3239.61, 2052.87]]
+        shapely_multipolygon = get_shapely_multipolygon(coco_segmentation)
+        self.assertTrue(shapely_multipolygon.is_valid)
+
     def test_shapely_annotation(self):
         # init shapely_annotation from coco segmentation
         segmentation = [[1, 1, 325, 125.2, 250, 200, 5, 200]]