fix(line_zone): tracker-id reuse across classes

supervision/detection/line_zone.py

@@ -99,7 +99,7 @@ def __init__(
         self.vector = Vector(start=start, end=end)
         self.limits = self._calculate_region_of_interest_limits(vector=self.vector)
         self.crossing_history_length = max(2, minimum_crossing_threshold + 1)
-        self.crossing_state_history: Dict[int, Deque[bool]] = defaultdict(
+        self.crossing_state_history: Dict[Tuple[int, int], Deque[bool]] = defaultdict(
             lambda: deque(maxlen=self.crossing_history_length)
         )
         self._in_count_per_class: Counter = Counter()
@@ -176,16 +176,12 @@ def trigger(self, detections: Detections) -> Tuple[np.ndarray, np.ndarray]:
                 continue
 
             tracker_state: bool = has_any_left_trigger[i]
-            crossing_history = self.crossing_state_history[tracker_id]
+            crossing_history = self.crossing_state_history[(tracker_id, class_id)]
             crossing_history.append(tracker_state)
 
             if len(crossing_history) < self.crossing_history_length:
                 continue
 
-            # TODO: Account for incorrect class_id.
-            #   Most likely this would involve indexing self.crossing_state_history
-            #   with (tracker_id, class_id).
-
             oldest_state = crossing_history[0]
             if crossing_history.count(oldest_state) > 1:
                 continue

supervision/utils/image.py

@@ -785,4 +785,4 @@ def _merge_tiles_elements(
 def _generate_color_image(
     shape: Tuple[int, int], color: Tuple[int, int, int]
 ) -> np.ndarray:
-    return np.ones(shape[::-1] + (3,), dtype=np.uint8) * color
+    return np.ones((*shape[::-1], 3), dtype=np.uint8) * color

test/detection/test_line_counter.py

@@ -776,3 +776,54 @@ def test_line_zone_long_horizon_disappearing_detections(
         assert crossed_out_list == expected_crossed_out
         assert count_in_list == expected_count_in
         assert count_out_list == expected_count_out
+
+
+def test_line_zone_tracker_id_reuse_with_different_classes() -> None:
+    line_zone = LineZone(start=Point(0, 0), end=Point(10, 0))
+
+    # First object with class 0 crosses the line
+    detections = mock_detections(
+        xyxy=[[4, 4, 6, 6]],
+        tracker_id=[0],
+        class_id=[0],
+    )
+    line_zone.trigger(detections)
+
+    detections = mock_detections(
+        xyxy=[[4, -6, 6, -4]],
+        tracker_id=[0],
+        class_id=[0],
+    )
+    line_zone.trigger(detections)
+
+    detections = mock_detections(
+        xyxy=[[4, 4, 6, 6]],
+        tracker_id=[0],
+        class_id=[0],
+    )
+    line_zone.trigger(detections)
+
+    # Second object reuses tracker id with a different class
+    detections = mock_detections(
+        xyxy=[[4, 4, 6, 6]],
+        tracker_id=[0],
+        class_id=[1],
+    )
+    line_zone.trigger(detections)
+
+    detections = mock_detections(
+        xyxy=[[4, -6, 6, -4]],
+        tracker_id=[0],
+        class_id=[1],
+    )
+    line_zone.trigger(detections)
+
+    detections = mock_detections(
+        xyxy=[[4, 4, 6, 6]],
+        tracker_id=[0],
+        class_id=[1],
+    )
+    line_zone.trigger(detections)
+
+    assert line_zone.in_count_per_class == {0: 1, 1: 1}
+    assert line_zone.out_count_per_class == {0: 1, 1: 1}