Fix in filter_bboxes (#1949)

.pre-commit-config.yaml

@@ -42,9 +42,16 @@ repos:
       entry: python tools/check_docstrings.py
       language: system
       types: [python]
+  - repo: local
+    hooks:
+      - id: check-albucore-version
+        name: Check albucore version
+        entry: python ./tools/check_albucore_version.py
+        language: system
+        files: setup.py
   - repo: https://github.com/astral-sh/ruff-pre-commit
     # Ruff version.
-    rev: v0.6.6
+    rev: v0.6.7
     hooks:
       # Run the linter.
       - id: ruff

albumentations/core/bbox_utils.py

@@ -445,7 +445,7 @@ def filter_bboxes(
     epsilon = 1e-7
 
     if len(bboxes) == 0:
-        return np.array([], dtype=np.float32)
+        return np.array([], dtype=np.float32).reshape(0, 4)
 
     # Calculate areas of bounding boxes before clipping in pixels
     denormalized_box_areas = calculate_bbox_areas_in_pixels(bboxes, image_shape)
@@ -474,8 +474,7 @@ def filter_bboxes(
     # Apply the mask to get the filtered bboxes
     filtered_bboxes = clipped_bboxes[mask]
 
-    # If no bboxes pass the filter, return an empty array with the same number of columns as input
-    return filtered_bboxes if len(filtered_bboxes) > 0 else np.array([], dtype=np.float32)
+    return np.array([], dtype=np.float32).reshape(0, 4) if len(filtered_bboxes) == 0 else filtered_bboxes
 
 
 def union_of_bboxes(bboxes: np.ndarray, erosion_rate: float) -> np.ndarray | None:

tests/test_bbox.py

@@ -494,7 +494,7 @@ def test_check_bboxes_additional_columns():
         np.array([[0.1, 0.1, 0.2, 0.2], [0.3, 0.3, 0.4, 0.4], [0.5, 0.5, 0.6, 0.6]]),
         (100, 100),
         200, 0, 0, 0,
-        np.array([])
+        np.array([]).reshape(0, 4)
     ),
     (
         np.array([[0.1, 0.1, 0.2, 0.2], [0.3, 0.3, 0.4, 0.4], [0.5, 0.5, 0.6, 0.6]]),
@@ -524,14 +524,20 @@ def test_check_bboxes_additional_columns():
         np.array([[0.1, 0.1, 0.2, 0.2, 1], [0.3, 0.3, 0.4, 0.4, 2], [0.5, 0.5, 0.6, 0.7, 3]]),
         (100, 100),
         300, 0, 0, 0,
-        np.array([])
+        np.array([]).reshape(0, 4)
     ),
     (
         np.array([]),
         (100, 100),
         0, 0, 0, 0,
-        np.array([])
+        np.array([]).reshape(0, 4)
     ),
+    (
+        np.array([[0.1, 0.1, 0.2, 0.2]]),
+        (100, 100),
+        101, 0, 0, 0,
+        np.array([]).reshape(0, 4)
+    )
 ])
 def test_filter_bboxes(bboxes, image_shape, min_area, min_visibility, min_width, min_height, expected):
     result = filter_bboxes(bboxes, image_shape, min_area, min_visibility, min_width, min_height)