Merge pull request #1228 from tc360950/vectorize-line-zone

Vectorize line zone

supervision/detection/line_zone.py

@@ -5,6 +5,7 @@
 import numpy as np
 
 from supervision.detection.core import Detections
+from supervision.detection.utils import cross_product
 from supervision.draw.color import Color
 from supervision.draw.utils import draw_text
 from supervision.geometry.core import Point, Position, Vector
@@ -158,28 +159,23 @@ def trigger(self, detections: Detections) -> Tuple[np.ndarray, np.ndarray]:
             ]
         )
 
-        for i, tracker_id in enumerate(detections.tracker_id):
-            box_anchors = [Point(x=x, y=y) for x, y in all_anchors[:, i, :]]
-
-            in_limits = all(
-                [
-                    self.is_point_in_limits(point=anchor, limits=self.limits)
-                    for anchor in box_anchors
-                ]
-            )
+        cross_products_1 = cross_product(all_anchors, self.limits[0])
+        cross_products_2 = cross_product(all_anchors, self.limits[1])
+        in_limits = (cross_products_1 > 0) == (cross_products_2 > 0)
+        in_limits = np.all(in_limits, axis=0)
 
-            if not in_limits:
+        triggers = cross_product(all_anchors, self.vector) < 0
+        has_any_left_trigger = np.any(triggers, axis=0)
+        has_any_right_trigger = np.any(~triggers, axis=0)
+        is_uniformly_triggered = ~(has_any_left_trigger & has_any_right_trigger)
+        for i, tracker_id in enumerate(detections.tracker_id):
+            if not in_limits[i]:
                 continue
 
-            triggers = [
-                self.vector.cross_product(point=anchor) < 0 for anchor in box_anchors
-            ]
-
-            if len(set(triggers)) == 2:
+            if not is_uniformly_triggered[i]:
                 continue
 
-            tracker_state = triggers[0]
-
+            tracker_state = has_any_left_trigger[i]
             if tracker_id not in self.tracker_state:
                 self.tracker_state[tracker_id] = tracker_state
                 continue

supervision/detection/utils.py

@@ -6,6 +6,7 @@
 import numpy.typing as npt
 
 from supervision.config import CLASS_NAME_DATA_FIELD
+from supervision.geometry.core import Vector
 
 MIN_POLYGON_POINT_COUNT = 3
 
@@ -833,3 +834,20 @@ def contains_multiple_segments(
         mask_uint8, labels, connectivity=connectivity
     )
     return number_of_labels > 2
+
+
+def cross_product(anchors: np.ndarray, vector: Vector) -> np.ndarray:
+    """
+    Get array of cross products of each anchor with a vector.
+    Args:
+        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)
+    """
+    vector_at_zero = np.array(
+        [vector.end.x - vector.start.x, vector.end.y - vector.start.y]
+    )
+    vector_start = np.array([vector.start.x, vector.start.y])
+    return np.cross(vector_at_zero, anchors - vector_start)