fix: prevent single object from appearing in multiple polygon zones (#1991)
* fix: prevent single object from appearing in multiple polygon zones when checking if a detection is inside a polygon zone, the previous implementation would clip the bounding box to fit within each ROI's dimensions before calculating anchor points. This caused the same detection to produce different anchor points for different ROIs, allowing it to be counted as present in multiple zones. * Add regression test for PolygonZone trigger issue #1987 and remove unused `frame_resolution_wh` attribute * refactor(polygon_zone): vectorize trigger() and strengthen tests Replace the O(n×m) Python double-loop in PolygonZone.trigger() with vectorized NumPy. Semantics are identical: compute a (num_anchors, num_detections) in_bounds mask, use np.clip solely for safe fancy-index access, then AND with the polygon mask and reduce with np.all(axis=0). Also removes the now-unused `from dataclasses import replace` import and a latent np.all(axis=1) call on a 1D array. Test improvements: - Group into TestPolygonZoneInit / TestPolygonZoneTrigger classes - Replace the trivially-passing regression (sum=0 on both old and new code) with adjacent zones + straddling detection that gives sum=2 on the old clip_boxes implementation and sum=1 on the fix - Rename tests to describe behaviour, not issue numbers - Add test_out_of_bounds_anchor_excluded and test_anchor_on_polygon_boundary_included edge cases * test(polygon_zone): verify current_count updates with expected results during trigger --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: jirka <6035284+Borda@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Adithi Sreenath
GitHub
parent
ca9bff184c
commit
c010656161
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@ -1,7 +1,6 @@
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from __future__ import annotations
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from collections.abc import Iterable
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from dataclasses import replace
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from typing import Any, cast
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import cv2
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@ -9,7 +8,6 @@ import numpy as np
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import numpy.typing as npt
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from supervision import Detections
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from supervision.detection.utils.boxes import clip_boxes
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from supervision.detection.utils.converters import polygon_to_mask
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from supervision.draw.color import Color
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from supervision.draw.utils import draw_filled_polygon, draw_polygon, draw_text
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@ -73,7 +71,6 @@ class PolygonZone:
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self.current_count = 0
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x_max, y_max = np.max(polygon, axis=0)
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self.frame_resolution_wh = (x_max + 1, y_max + 1)
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self.mask = polygon_to_mask(
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polygon=polygon, resolution_wh=(x_max + 2, y_max + 2)
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)
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@ -82,33 +79,36 @@ class PolygonZone:
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"""
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Determines if the detections are within the polygon zone.
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Anchor points are calculated from original (unclipped) detection boxes to
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avoid per-zone clipping shifting anchor positions. This prevents a single
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detection from being counted in multiple non-overlapping zones due to
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clipping artifacts, although overlapping zones may still legitimately
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contain the same detection.
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Args:
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detections: The detections
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to be checked against the polygon zone
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detections: The detections to be checked against the polygon zone
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Returns:
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A boolean numpy array indicating
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if each detection is within the polygon zone
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"""
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if len(detections) == 0:
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self.current_count = 0
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return np.array([], dtype=bool)
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clipped_xyxy = clip_boxes(
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xyxy=detections.xyxy, resolution_wh=self.frame_resolution_wh
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)
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clipped_detections = replace(detections, xyxy=clipped_xyxy)
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all_clipped_anchors = np.array(
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all_anchors = np.array(
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[
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np.ceil(clipped_detections.get_anchors_coordinates(anchor)).astype(int)
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for anchor in self.triggering_anchors
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np.ceil(detections.get_anchors_coordinates(anchors)).astype(int)
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for anchors in self.triggering_anchors
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]
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)
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is_in_zone: npt.NDArray[np.bool_] = (
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self.mask[all_clipped_anchors[:, :, 1], all_clipped_anchors[:, :, 0]]
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.transpose()
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.astype(bool)
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)
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is_in_zone = np.all(is_in_zone, axis=1)
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mask_h, mask_w = self.mask.shape
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x, y = all_anchors[:, :, 0], all_anchors[:, :, 1]
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in_bounds = (x >= 0) & (y >= 0) & (x < mask_w) & (y < mask_h)
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x_safe = np.clip(x, 0, mask_w - 1)
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y_safe = np.clip(y, 0, mask_h - 1)
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is_in_zone = np.all(in_bounds & self.mask[y_safe, x_safe], axis=0)
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self.current_count = int(np.sum(is_in_zone))
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return is_in_zone.astype(bool)
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@ -28,78 +28,139 @@ DETECTIONS = _create_detections(
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POLYGON = np.array([[100, 100], [200, 100], [200, 200], [100, 200]])
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@pytest.mark.parametrize(
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("detections", "polygon_zone", "expected_results", "exception"),
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[
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(
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DETECTIONS,
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sv.PolygonZone(
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class TestPolygonZoneInit:
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@pytest.mark.parametrize(
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("polygon", "triggering_anchors", "exception"),
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[
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(POLYGON, [sv.Position.CENTER], DoesNotRaise()),
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(
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POLYGON,
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triggering_anchors=(
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sv.Position.TOP_LEFT,
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sv.Position.TOP_RIGHT,
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sv.Position.BOTTOM_LEFT,
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sv.Position.BOTTOM_RIGHT,
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[],
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pytest.raises(ValueError, match="Triggering anchors cannot be empty"),
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),
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],
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)
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def test_empty_anchors_raises(self, polygon, triggering_anchors, exception):
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with exception:
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sv.PolygonZone(polygon, triggering_anchors=triggering_anchors)
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class TestPolygonZoneTrigger:
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@pytest.mark.parametrize(
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("detections", "polygon_zone", "expected_results", "exception"),
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[
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(
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DETECTIONS,
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sv.PolygonZone(
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POLYGON,
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triggering_anchors=(
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sv.Position.TOP_LEFT,
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sv.Position.TOP_RIGHT,
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sv.Position.BOTTOM_LEFT,
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sv.Position.BOTTOM_RIGHT,
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),
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),
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),
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np.array(
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[False, False, False, True, True, True, False, False, False], dtype=bool
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),
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DoesNotRaise(),
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), # Test all four corners
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(
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DETECTIONS,
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sv.PolygonZone(
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POLYGON,
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),
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np.array(
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[False, False, True, True, True, True, False, False, False], dtype=bool
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),
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DoesNotRaise(),
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), # Test default behaviour when no anchors are provided
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(
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DETECTIONS,
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sv.PolygonZone(
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POLYGON,
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triggering_anchors=[sv.Position.BOTTOM_CENTER],
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),
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np.array(
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[False, False, True, True, True, True, False, False, False], dtype=bool
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),
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DoesNotRaise(),
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), # Test default behaviour with deprecated api.
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(
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sv.Detections.empty(),
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sv.PolygonZone(
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POLYGON,
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),
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np.array([], dtype=bool),
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DoesNotRaise(),
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), # Test empty detections
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],
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)
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def test_polygon_zone_trigger(
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detections: sv.Detections,
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polygon_zone: sv.PolygonZone,
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expected_results: np.ndarray,
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exception: Exception,
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) -> None:
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with exception:
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in_zone = polygon_zone.trigger(detections)
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assert np.all(in_zone == expected_results)
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np.array(
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[False, False, False, True, True, True, False, False, False],
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dtype=bool,
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),
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DoesNotRaise(),
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), # all four corners must be inside
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(
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DETECTIONS,
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sv.PolygonZone(POLYGON),
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np.array(
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[False, False, True, True, True, True, False, False, False],
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dtype=bool,
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),
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DoesNotRaise(),
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), # default anchor (BOTTOM_CENTER)
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(
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DETECTIONS,
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sv.PolygonZone(
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POLYGON,
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triggering_anchors=[sv.Position.BOTTOM_CENTER],
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),
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np.array(
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[False, False, True, True, True, True, False, False, False],
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dtype=bool,
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),
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DoesNotRaise(),
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), # explicit BOTTOM_CENTER matches default
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(
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sv.Detections.empty(),
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sv.PolygonZone(POLYGON),
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np.array([], dtype=bool),
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DoesNotRaise(),
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), # empty detections return empty array
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],
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)
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def test_anchor_configurations(
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self,
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detections: sv.Detections,
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polygon_zone: sv.PolygonZone,
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expected_results: np.ndarray,
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exception: Exception,
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) -> None:
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with exception:
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in_zone = polygon_zone.trigger(detections)
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assert np.all(in_zone == expected_results)
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assert polygon_zone.current_count == int(np.sum(expected_results))
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def test_straddling_detection_assigned_to_one_zone(self) -> None:
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"""Detection straddling two adjacent zones is counted in exactly one zone.
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@pytest.mark.parametrize(
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("polygon", "triggering_anchors", "exception"),
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[
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(POLYGON, [sv.Position.CENTER], DoesNotRaise()),
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(
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POLYGON,
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[],
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pytest.raises(ValueError, match="Triggering anchors cannot be empty"),
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),
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],
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)
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def test_polygon_zone_initialization(polygon, triggering_anchors, exception):
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with exception:
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sv.PolygonZone(polygon, triggering_anchors=triggering_anchors)
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The old implementation clipped each detection box to the zone's bounding box
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before computing anchors, so a box straddling two adjacent zones got a
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different anchor per zone and was double-counted. The fix computes anchors
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from the original unclipped box, giving a single consistent position.
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Setup: zone_left covers x 0-99, zone_right covers x 100-200.
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Detection [60, 80, 140, 120] has BOTTOM_CENTER = ceil((60+140)/2), ceil(120)
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= (100, 120), which falls in zone_right only.
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"""
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zone_left = sv.PolygonZone(
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np.array([[0, 0], [99, 0], [99, 200], [0, 200]], dtype=np.int32)
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)
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zone_right = sv.PolygonZone(
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np.array([[100, 0], [200, 0], [200, 200], [100, 200]], dtype=np.int32)
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)
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detections = _create_detections(
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xyxy=[[60.0, 80.0, 140.0, 120.0]],
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class_id=[0],
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)
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results = np.array(
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[zone.trigger(detections)[0] for zone in [zone_left, zone_right]],
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dtype=bool,
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)
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assert np.sum(results) == 1, (
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"Detection should appear in exactly one zone, not zero or multiple"
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)
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assert results[1], "BOTTOM_CENTER (100, 120) should be in zone_right"
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def test_out_of_bounds_anchor_excluded(self) -> None:
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"""Anchors with negative coordinates are excluded, not wrapped or clamped."""
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zone = sv.PolygonZone(
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np.array([[0, 0], [100, 0], [100, 100], [0, 100]]),
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triggering_anchors=[sv.Position.CENTER],
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)
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# CENTER = (ceil((-50+0)/2), ceil((25+75)/2)) = (-25, 50) — x < 0.
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detections = _create_detections(
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xyxy=[[-50.0, 25.0, 0.0, 75.0]],
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class_id=[0],
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)
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result = zone.trigger(detections)
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assert not result[0]
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def test_anchor_on_polygon_boundary_included(self) -> None:
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"""An anchor landing exactly on a polygon corner is counted as inside."""
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polygon = np.array([[0, 0], [100, 0], [100, 100], [0, 100]])
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zone = sv.PolygonZone(polygon, triggering_anchors=[sv.Position.BOTTOM_RIGHT])
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# BOTTOM_RIGHT = (ceil(x2), ceil(y2)) = (100, 100) — the polygon corner.
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detections = _create_detections(
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xyxy=[[50.0, 50.0, 100.0, 100.0]],
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class_id=[0],
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)
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result = zone.trigger(detections)
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assert result[0]
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