Cleanup tracker and remove unused functions (#4374)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/trackers/utils/kalman_filter.py

@@ -3,10 +3,6 @@
 import numpy as np
 import scipy.linalg
 
-# Table for the 0.95 quantile of the chi-square distribution with N degrees of freedom (contains values for N=1, ..., 9)
-# Taken from MATLAB/Octave's chi2inv function and used as Mahalanobis gating threshold.
-chi2inv95 = {1: 3.8415, 2: 5.9915, 3: 7.8147, 4: 9.4877, 5: 11.070, 6: 12.592, 7: 14.067, 8: 15.507, 9: 16.919}
-
 
 class KalmanFilterXYAH:
     """
@@ -235,7 +231,7 @@ class KalmanFilterXYAH:
             raise ValueError('invalid distance metric')
 
 
-class KalmanFilterXYWH:
+class KalmanFilterXYWH(KalmanFilterXYAH):
     """
     For BoT-SORT
     A simple Kalman filter for tracking bounding boxes in image space.
@@ -253,22 +249,6 @@ class KalmanFilterXYWH:
 
     """
 
-    def __init__(self):
-        """Initialize Kalman filter model matrices with motion and observation uncertainties."""
-        ndim, dt = 4, 1.
-
-        # Create Kalman filter model matrices.
-        self._motion_mat = np.eye(2 * ndim, 2 * ndim)
-        for i in range(ndim):
-            self._motion_mat[i, ndim + i] = dt
-        self._update_mat = np.eye(ndim, 2 * ndim)
-
-        # Motion and observation uncertainty are chosen relative to the current
-        # state estimate. These weights control the amount of uncertainty in
-        # the model. This is a bit hacky.
-        self._std_weight_position = 1. / 20
-        self._std_weight_velocity = 1. / 160
-
     def initiate(self, measurement):
         """Create track from unassociated measurement.
 
@@ -409,54 +389,4 @@ class KalmanFilterXYWH:
             Returns the measurement-corrected state distribution.
 
         """
-        projected_mean, projected_cov = self.project(mean, covariance)
+        return super().update(mean, covariance, measurement)
-
-        chol_factor, lower = scipy.linalg.cho_factor(projected_cov, lower=True, check_finite=False)
-        kalman_gain = scipy.linalg.cho_solve((chol_factor, lower),
-                                             np.dot(covariance, self._update_mat.T).T,
-                                             check_finite=False).T
-        innovation = measurement - projected_mean
-
-        new_mean = mean + np.dot(innovation, kalman_gain.T)
-        new_covariance = covariance - np.linalg.multi_dot((kalman_gain, projected_cov, kalman_gain.T))
-        return new_mean, new_covariance
-
-    def gating_distance(self, mean, covariance, measurements, only_position=False, metric='maha'):
-        """Compute gating distance between state distribution and measurements.
-        A suitable distance threshold can be obtained from `chi2inv95`. If
-        `only_position` is False, the chi-square distribution has 4 degrees of
-        freedom, otherwise 2.
-        Parameters
-        ----------
-        mean : ndarray
-            Mean vector over the state distribution (8 dimensional).
-        covariance : ndarray
-            Covariance of the state distribution (8x8 dimensional).
-        measurements : ndarray
-            An Nx4 dimensional matrix of N measurements, each in
-            format (x, y, a, h) where (x, y) is the bounding box center
-            position, a the aspect ratio, and h the height.
-        only_position : Optional[bool]
-            If True, distance computation is done with respect to the bounding
-            box center position only.
-        Returns
-        -------
-        ndarray
-            Returns an array of length N, where the i-th element contains the
-            squared Mahalanobis distance between (mean, covariance) and
-            `measurements[i]`.
-        """
-        mean, covariance = self.project(mean, covariance)
-        if only_position:
-            mean, covariance = mean[:2], covariance[:2, :2]
-            measurements = measurements[:, :2]
-
-        d = measurements - mean
-        if metric == 'gaussian':
-            return np.sum(d * d, axis=1)
-        elif metric == 'maha':
-            cholesky_factor = np.linalg.cholesky(covariance)
-            z = scipy.linalg.solve_triangular(cholesky_factor, d.T, lower=True, check_finite=False, overwrite_b=True)
-            return np.sum(z * z, axis=0)  # square maha
-        else:
-            raise ValueError('invalid distance metric')

ultralytics/trackers/utils/matching.py

@@ -4,7 +4,7 @@ import numpy as np
 import scipy
 from scipy.spatial.distance import cdist
 
-from .kalman_filter import chi2inv95
+from ultralytics.utils.metrics import bbox_ioa
 
 try:
     import lap  # for linear_assignment
@@ -17,36 +17,6 @@ except (ImportError, AssertionError, AttributeError):
     import lap
 
 
-def merge_matches(m1, m2, shape):
-    """Merge two sets of matches and return matched and unmatched indices."""
-    O, P, Q = shape
-    m1 = np.asarray(m1)
-    m2 = np.asarray(m2)
-
-    M1 = scipy.sparse.coo_matrix((np.ones(len(m1)), (m1[:, 0], m1[:, 1])), shape=(O, P))
-    M2 = scipy.sparse.coo_matrix((np.ones(len(m2)), (m2[:, 0], m2[:, 1])), shape=(P, Q))
-
-    mask = M1 * M2
-    match = mask.nonzero()
-    match = list(zip(match[0], match[1]))
-    unmatched_O = tuple(set(range(O)) - {i for i, j in match})
-    unmatched_Q = tuple(set(range(Q)) - {j for i, j in match})
-
-    return match, unmatched_O, unmatched_Q
-
-
-def _indices_to_matches(cost_matrix, indices, thresh):
-    """Return matched and unmatched indices given a cost matrix, indices, and a threshold."""
-    matched_cost = cost_matrix[tuple(zip(*indices))]
-    matched_mask = (matched_cost <= thresh)
-
-    matches = indices[matched_mask]
-    unmatched_a = tuple(set(range(cost_matrix.shape[0])) - set(matches[:, 0]))
-    unmatched_b = tuple(set(range(cost_matrix.shape[1])) - set(matches[:, 1]))
-
-    return matches, unmatched_a, unmatched_b
-
-
 def linear_assignment(cost_matrix, thresh, use_lap=True):
     """Linear assignment implementations with scipy and lap.lapjv."""
     if cost_matrix.size == 0:
@@ -70,26 +40,6 @@ def linear_assignment(cost_matrix, thresh, use_lap=True):
     return matches, unmatched_a, unmatched_b
 
 
-def ious(atlbrs, btlbrs):
-    """
-    Compute cost based on IoU
-    :type atlbrs: list[tlbr] | np.ndarray
-    :type atlbrs: list[tlbr] | np.ndarray
-
-    :rtype ious np.ndarray
-    """
-    ious = np.zeros((len(atlbrs), len(btlbrs)), dtype=np.float32)
-    if ious.size == 0:
-        return ious
-    ious = bbox_ious(np.ascontiguousarray(atlbrs, dtype=np.float32), np.ascontiguousarray(btlbrs, dtype=np.float32))
-
-    # TODO: replace bbox_ious() with numpy-capable update of utils.metrics.box_iou
-    # from ...utils.metrics import box_iou
-    # ious = box_iou()
-
-    return ious
-
-
 def iou_distance(atracks, btracks):
     """
     Compute cost based on IoU
@@ -106,26 +56,13 @@ def iou_distance(atracks, btracks):
     else:
         atlbrs = [track.tlbr for track in atracks]
         btlbrs = [track.tlbr for track in btracks]
-    return 1 - ious(atlbrs, btlbrs)  # cost matrix
-
-
-def v_iou_distance(atracks, btracks):
-    """
-    Compute cost based on IoU
-    :type atracks: list[STrack]
-    :type btracks: list[STrack]
 
-    :rtype cost_matrix np.ndarray
+    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),
-    if (len(atracks) > 0 and isinstance(atracks[0], np.ndarray)) \
+                        np.ascontiguousarray(btlbrs, dtype=np.float32),
-            or (len(btracks) > 0 and isinstance(btracks[0], np.ndarray)):
+                        iou=True)
-        atlbrs = atracks
+    return 1 - ious  # cost matrix
-        btlbrs = btracks
-    else:
-        atlbrs = [track.tlwh_to_tlbr(track.pred_bbox) for track in atracks]
-        btlbrs = [track.tlwh_to_tlbr(track.pred_bbox) for track in btracks]
-    return 1 - ious(atlbrs, btlbrs)  # cost matrix
 
 
 def embedding_distance(tracks, detections, metric='cosine'):
@@ -147,46 +84,6 @@ def embedding_distance(tracks, detections, metric='cosine'):
     return cost_matrix
 
 
-def gate_cost_matrix(kf, cost_matrix, tracks, detections, only_position=False):
-    """Apply gating to the cost matrix based on predicted tracks and detected objects."""
-    if cost_matrix.size == 0:
-        return cost_matrix
-    gating_dim = 2 if only_position else 4
-    gating_threshold = chi2inv95[gating_dim]
-    measurements = np.asarray([det.to_xyah() for det in detections])
-    for row, track in enumerate(tracks):
-        gating_distance = kf.gating_distance(track.mean, track.covariance, measurements, only_position)
-        cost_matrix[row, gating_distance > gating_threshold] = np.inf
-    return cost_matrix
-
-
-def fuse_motion(kf, cost_matrix, tracks, detections, only_position=False, lambda_=0.98):
-    """Fuse motion between tracks and detections with gating and Kalman filtering."""
-    if cost_matrix.size == 0:
-        return cost_matrix
-    gating_dim = 2 if only_position else 4
-    gating_threshold = chi2inv95[gating_dim]
-    measurements = np.asarray([det.to_xyah() for det in detections])
-    for row, track in enumerate(tracks):
-        gating_distance = kf.gating_distance(track.mean, track.covariance, measurements, only_position, metric='maha')
-        cost_matrix[row, gating_distance > gating_threshold] = np.inf
-        cost_matrix[row] = lambda_ * cost_matrix[row] + (1 - lambda_) * gating_distance
-    return cost_matrix
-
-
-def fuse_iou(cost_matrix, tracks, detections):
-    """Fuses ReID and IoU similarity matrices to yield a cost matrix for object tracking."""
-    if cost_matrix.size == 0:
-        return cost_matrix
-    reid_sim = 1 - cost_matrix
-    iou_dist = iou_distance(tracks, detections)
-    iou_sim = 1 - iou_dist
-    fuse_sim = reid_sim * (1 + iou_sim) / 2
-    # 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)
-    return 1 - fuse_sim  # fuse cost
-
-
 def fuse_score(cost_matrix, detections):
     """Fuses cost matrix with detection scores to produce a single similarity matrix."""
     if cost_matrix.size == 0:
@@ -196,36 +93,3 @@ def fuse_score(cost_matrix, 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
-
-
-def bbox_ious(box1, box2, eps=1e-7):
-    """
-    Calculate the Intersection over Union (IoU) between pairs of bounding boxes.
-
-    Args:
-        box1 (np.array): A numpy array of shape (n, 4) representing 'n' bounding boxes.
-                         Each row is in the format (x1, y1, x2, y2).
-        box2 (np.array): A numpy array of shape (m, 4) representing 'm' bounding boxes.
-                         Each row is in the format (x1, y1, x2, y2).
-        eps (float, optional): A small constant to prevent division by zero. Defaults to 1e-7.
-
-    Returns:
-        (np.array): A numpy array of shape (n, m) representing the IoU scores for each pair
-                    of bounding boxes from box1 and box2.
-
-    Note:
-        The bounding box coordinates are expected to be in the format (x1, y1, x2, y2).
-    """
-
-    # Get the coordinates of bounding boxes
-    b1_x1, b1_y1, b1_x2, b1_y2 = box1.T
-    b2_x1, b2_y1, b2_x2, b2_y2 = box2.T
-
-    # Intersection area
-    inter_area = (np.minimum(b1_x2[:, None], b2_x2) - np.maximum(b1_x1[:, None], b2_x1)).clip(0) * \
-                 (np.minimum(b1_y2[:, None], b2_y2) - np.maximum(b1_y1[:, None], b2_y1)).clip(0)
-
-    # box2 area
-    box1_area = (b1_x2 - b1_x1) * (b1_y2 - b1_y1)
-    box2_area = (b2_x2 - b2_x1) * (b2_y2 - b2_y1)
-    return inter_area / (box2_area + box1_area[:, None] - inter_area + eps)

ultralytics/utils/metrics.py

@@ -21,13 +21,14 @@ def box_area(box):
     return (box[2] - box[0]) * (box[3] - box[1])
 
 
-def bbox_ioa(box1, box2, eps=1e-7):
+def bbox_ioa(box1, box2, iou=False, eps=1e-7):
     """
     Calculate the intersection over box2 area given box1 and box2. Boxes are in x1y1x2y2 format.
 
     Args:
         box1 (np.array): A numpy array of shape (n, 4) representing n bounding boxes.
         box2 (np.array): A numpy array of shape (m, 4) representing m bounding boxes.
+        iou (bool): Calculate the standard iou if True else return inter_area/box2_area.
         eps (float, optional): A small value to avoid division by zero. Defaults to 1e-7.
 
     Returns:
@@ -43,10 +44,13 @@ def bbox_ioa(box1, box2, eps=1e-7):
                  (np.minimum(b1_y2[:, None], b2_y2) - np.maximum(b1_y1[:, None], b2_y1)).clip(0)
 
     # box2 area
-    box2_area = (b2_x2 - b2_x1) * (b2_y2 - b2_y1) + eps
+    area = (b2_x2 - b2_x1) * (b2_y2 - b2_y1)
+    if iou:
+        box1_area = (b1_x2 - b1_x1) * (b1_y2 - b1_y1)
+        area = area + box1_area[:, None] - inter_area
 
     # Intersection over box2 area
-    return inter_area / box2_area
+    return inter_area / (area + eps)
 
 
 def box_iou(box1, box2, eps=1e-7):