update

ytracking/ultralytics/trackers/utils/matching.py

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+# Ultralytics YOLO 🚀, AGPL-3.0 license
+
+import numpy as np
+import scipy
+from scipy.spatial.distance import cdist
+
+from ultralytics.utils.metrics import bbox_ioa
+
+try:
+    import lap  # for linear_assignment
+
+    assert lap.__version__  # verify package is not directory
+except (ImportError, AssertionError, AttributeError):
+    from ultralytics.utils.checks import check_requirements
+
+    check_requirements('lapx>=0.5.2')  # update to lap package from https://github.com/rathaROG/lapx
+    import lap
+
+
+def linear_assignment(cost_matrix, thresh, use_lap=True):
+    """
+    Perform linear assignment using scipy or lap.lapjv.
+
+    Args:
+        cost_matrix (np.ndarray): The matrix containing cost values for assignments.
+        thresh (float): Threshold for considering an assignment valid.
+        use_lap (bool, optional): Whether to use lap.lapjv. Defaults to True.
+
+    Returns:
+        (tuple): Tuple containing matched indices, unmatched indices from 'a', and unmatched indices from 'b'.
+    """
+
+    if cost_matrix.size == 0:
+        return np.empty((0, 2), dtype=int), tuple(range(cost_matrix.shape[0])), tuple(range(cost_matrix.shape[1]))
+
+    if use_lap:
+        # https://github.com/gatagat/lap
+        _, x, y = lap.lapjv(cost_matrix, extend_cost=True, cost_limit=thresh)
+        matches = [[ix, mx] for ix, mx in enumerate(x) if mx >= 0]
+        unmatched_a = np.where(x < 0)[0]
+        unmatched_b = np.where(y < 0)[0]
+    else:
+        # https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.linear_sum_assignment.html
+        x, y = scipy.optimize.linear_sum_assignment(cost_matrix)  # row x, col y
+        matches = np.asarray([[x[i], y[i]] for i in range(len(x)) if cost_matrix[x[i], y[i]] <= thresh])
+        if len(matches) == 0:
+            unmatched_a = list(np.arange(cost_matrix.shape[0]))
+            unmatched_b = list(np.arange(cost_matrix.shape[1]))
+        else:
+            unmatched_a = list(set(np.arange(cost_matrix.shape[0])) - set(matches[:, 0]))
+            unmatched_b = list(set(np.arange(cost_matrix.shape[1])) - set(matches[:, 1]))
+
+    return matches, unmatched_a, unmatched_b
+
+
+def iou_distance(atracks, btracks):
+    """
+    Compute cost based on Intersection over Union (IoU) between tracks.
+
+    Args:
+        atracks (list[STrack] | list[np.ndarray]): List of tracks 'a' or bounding boxes.
+        btracks (list[STrack] | list[np.ndarray]): List of tracks 'b' or bounding boxes.
+
+    Returns:
+        (np.ndarray): Cost matrix computed based on IoU.
+    """
+
+    if (len(atracks) > 0 and isinstance(atracks[0], np.ndarray)) \
+            or (len(btracks) > 0 and isinstance(btracks[0], np.ndarray)):
+        atlbrs = atracks
+        btlbrs = btracks
+    else:
+        atlbrs = [track.tlbr for track in atracks]
+        btlbrs = [track.tlbr for track in btracks]
+
+    ious = np.zeros((len(atlbrs), len(btlbrs)), dtype=np.float32)
+    if len(atlbrs) and len(btlbrs):
+        ious = bbox_ioa(np.ascontiguousarray(atlbrs, dtype=np.float32),
+                        np.ascontiguousarray(btlbrs, dtype=np.float32),
+                        iou=True)
+    return 1 - ious  # cost matrix
+
+
+def embedding_distance(tracks, detections, metric='cosine'):
+    """
+    Compute distance between tracks and detections based on embeddings.
+
+    Args:
+        tracks (list[STrack]): List of tracks.
+        detections (list[BaseTrack]): List of detections.
+        metric (str, optional): Metric for distance computation. Defaults to 'cosine'.
+
+    Returns:
+        (np.ndarray): Cost matrix computed based on embeddings.
+    """
+
+    cost_matrix = np.zeros((len(tracks), len(detections)), dtype=np.float32)
+    if cost_matrix.size == 0:
+        return cost_matrix
+    det_features = np.asarray([track.curr_feat for track in detections], dtype=np.float32)
+    # for i, track in enumerate(tracks):
+    # cost_matrix[i, :] = np.maximum(0.0, cdist(track.smooth_feat.reshape(1,-1), det_features, metric))
+    track_features = np.asarray([track.smooth_feat for track in tracks], dtype=np.float32)
+    cost_matrix = np.maximum(0.0, cdist(track_features, det_features, metric))  # Normalized features
+    return cost_matrix
+
+
+def fuse_score(cost_matrix, detections):
+    """
+    Fuses cost matrix with detection scores to produce a single similarity matrix.
+
+    Args:
+        cost_matrix (np.ndarray): The matrix containing cost values for assignments.
+        detections (list[BaseTrack]): List of detections with scores.
+
+    Returns:
+        (np.ndarray): Fused similarity matrix.
+    """
+
+    if cost_matrix.size == 0:
+        return cost_matrix
+    iou_sim = 1 - cost_matrix
+    det_scores = np.array([det.score for det in detections])
+    det_scores = np.expand_dims(det_scores, axis=0).repeat(cost_matrix.shape[0], axis=0)
+    fuse_sim = iou_sim * det_scores
+    return 1 - fuse_sim  # fuse_cost