fix: replace deprecated 2-D np.cross with explicit determinant (#2386)

- Add filterwarnings = ["error::DeprecationWarning"] to pyproject.toml so
  future np.cross 2-D reintroductions fail CI immediately (closes #2384)
- Add test_get_polygon_center_no_deprecation_warning: asserts no
  DeprecationWarning from get_polygon_center (Copilot inline comment)
- Add test_cross_product_no_deprecation_warning: asserts no DeprecationWarning
  from cross_product (Copilot inline comment)
- Add test_cross_product_sign (4 parametrised cases): above / below / on-line /
  offset-start — directly tests the inline determinant correctness
- Improve cross_product docstring: blank line after summary, adds Examples
  section with correct output, notes NumPy 2.0 rationale

---------

Co-authored-by: jirka <6035284+Borda@users.noreply.github.com>
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>

pyproject.toml

@@ -199,6 +199,9 @@ ini_options.addopts = [
   "--doctest-modules",
   "--color=yes",
 ]
+ini_options.filterwarnings = [
+  "error::DeprecationWarning",
+]
 ini_options.doctest_optionflags = "ELLIPSIS NORMALIZE_WHITESPACE"
 
 [tool.autoflake]

src/supervision/detection/utils/internal.py

@@ -653,14 +653,28 @@ def get_data_item(
 def cross_product(
     anchors: npt.NDArray[np.number], vector: Vector
 ) -> npt.NDArray[np.number]:
-    """
-    Get array of cross products of each anchor with a vector.
+    """Get signed z-component of cross product (2-D determinant) per anchor.
+
+    Replaces the deprecated `np.cross` 2-D path (NumPy 2.0) with an explicit
+    determinant: ``a[..., 0] * b[..., 1] - a[..., 1] * b[..., 0]``.
+
     Args:
-        anchors: Array of anchors of shape (number of anchors, detections, 2)
-        vector: Vector to calculate cross product with
+        anchors: Array of anchors of shape (number of anchors, detections, 2).
+        vector: Vector to calculate cross product with.
 
     Returns:
-        Array of cross products of shape (number of anchors, detections)
+        Array of signed cross-product values, shape (number of anchors,
+        detections). Positive = anchor is to the left of the vector direction;
+        negative = to the right; zero = on the line.
+
+    Examples:
+        >>> import numpy as np
+        >>> from supervision.geometry.core import Point, Vector
+        >>> anchors = np.array([[[10.0, 5.0]], [[20.0, 5.0]]])
+        >>> vector = Vector(start=Point(0, 0), end=Point(1, 0))
+        >>> cross_product(anchors, vector)
+        array([[5.],
+               [5.]])
     """
     vector_at_zero = np.array(
         [
@@ -669,6 +683,8 @@ def cross_product(
         ]
     )
     vector_start = np.array([vector.start.x, vector.start.y])
+    diff = anchors - vector_start
     return cast(
-        npt.NDArray[np.number], np.cross(vector_at_zero, anchors - vector_start)
+        npt.NDArray[np.number],
+        vector_at_zero[0] * diff[..., 1] - vector_at_zero[1] * diff[..., 0],
     )

src/supervision/geometry/utils.py

@@ -41,7 +41,10 @@ def get_polygon_center(polygon: npt.NDArray[np.float64]) -> Point:
         raise ValueError("Polygon must have at least one vertex.")
 
     shift_polygon = np.roll(polygon, -1, axis=0)
-    signed_areas = np.cross(polygon, shift_polygon) / 2
+    signed_areas = (
+        polygon[..., 0] * shift_polygon[..., 1]
+        - polygon[..., 1] * shift_polygon[..., 0]
+    ) / 2
     if signed_areas.sum() == 0:
         center = np.mean(polygon, axis=0).round()
         return Point(x=center[0], y=center[1])

tests/detection/test_line_counter.py

@@ -879,6 +879,26 @@ def test_line_zone_tracker_id_reuse_with_different_classes(
     assert line_zone.out_count_per_class == expected_out_count_per_class
 
 
+def test_line_zone_trigger_does_not_call_np_cross(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Guard against reintroducing np.cross, deprecated for 2-D input in NumPy 2.0."""
+
+    def _raise(*args, **kwargs):
+        raise AssertionError("np.cross must not be called on 2-D vectors")
+
+    monkeypatch.setattr(np, "cross", _raise)
+
+    line_zone = LineZone(start=Point(0, 0), end=Point(0, 10))
+    for xyxy in [[4, 4, 6, 6], [-6, 4, -4, 6]]:
+        detections = _create_detections(xyxy=[xyxy], tracker_id=[0])
+        crossed_in, crossed_out = line_zone.trigger(detections)
+
+    assert not crossed_in[0]
+    assert crossed_out[0]
+    assert line_zone.out_count == 1
+
+
 def test_line_zone_annotator_multiclass_supports_none_class_id() -> None:
     line_zone = LineZone(start=Point(0, 0), end=Point(0, 10))
     for xyxy in [[4, 4, 6, 6], [-6, 4, -4, 6]]:

tests/detection/utils/test_internal.py

@@ -1125,3 +1125,58 @@ def test_process_roboflow_result_compact_masks_rle_mask_size_mismatch() -> None:
 
     assert isinstance(compact_result[3], CompactMask)
     np.testing.assert_array_equal(compact_result[3].to_dense(), dense_result[3])
+
+
+# ---------------------------------------------------------------------------
+# cross_product — regression + unit tests (GitHub #2384)
+# ---------------------------------------------------------------------------
+import warnings  # noqa: E402
+
+from supervision.detection.utils.internal import cross_product  # noqa: E402
+from supervision.geometry.core import Point, Vector  # noqa: E402
+
+
+def test_cross_product_no_deprecation_warning() -> None:
+    """Regression for #2384: cross_product must not fire DeprecationWarning."""
+    anchors = np.array([[[5.0, 5.0]]])
+    v = Vector(start=Point(0, 0), end=Point(10, 0))
+    with warnings.catch_warnings():
+        warnings.simplefilter("error", DeprecationWarning)
+        cross_product(anchors, v)
+
+
+@pytest.mark.parametrize(
+    ("anchors", "vector", "expected_sign"),
+    [
+        pytest.param(
+            np.array([[[5.0, 5.0]]]),
+            Vector(Point(0, 0), Point(10, 0)),
+            1,
+            id="above",
+        ),
+        pytest.param(
+            np.array([[[5.0, -5.0]]]),
+            Vector(Point(0, 0), Point(10, 0)),
+            -1,
+            id="below",
+        ),
+        pytest.param(
+            np.array([[[5.0, 0.0]]]),
+            Vector(Point(0, 0), Point(10, 0)),
+            0,
+            id="on-line",
+        ),
+        pytest.param(
+            np.array([[[3.0, 3.0]]]),
+            Vector(Point(1, 1), Point(5, 1)),
+            1,
+            id="offset-start",
+        ),
+    ],
+)
+def test_cross_product_sign(
+    anchors: np.ndarray, vector: Vector, expected_sign: int
+) -> None:
+    """Verify cross_product returns correct sign for known anchor/vector pairs."""
+    result = cross_product(anchors, vector)
+    assert int(np.sign(result[0, 0])) == expected_sign

tests/geometry/test_utils.py

@@ -58,3 +58,28 @@ def test_get_polygon_center(polygon: np.ndarray, expected_result: Point) -> None
     """
     result = get_polygon_center(polygon)
     assert result == expected_result
+
+
+def test_get_polygon_center_no_deprecation_warning() -> None:
+    """Regression for #2384: get_polygon_center must not fire DeprecationWarning."""
+    import warnings
+
+    polygon = np.array([[0, 0], [0, 2], [2, 2], [2, 0]], dtype=float)
+    with warnings.catch_warnings():
+        warnings.simplefilter("error", DeprecationWarning)
+        get_polygon_center(polygon=polygon)
+
+
+def test_get_polygon_center_does_not_call_np_cross(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Guard against reintroducing np.cross, deprecated for 2-D input in NumPy 2.0."""
+
+    def _raise(*args, **kwargs):
+        raise AssertionError("np.cross must not be called on 2-D vectors")
+
+    monkeypatch.setattr(np, "cross", _raise)
+
+    result = get_polygon_center(generate_test_polygon(100))
+
+    assert result == Point(x=50.0, y=121.0)