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| 1 | +# vim: expandtab:ts=4:sw=4 |
| 2 | +from __future__ import absolute_import |
| 3 | +import numpy as np |
| 4 | +from . import linear_assignment |
| 5 | + |
| 6 | + |
| 7 | +def iou(bbox, candidates): |
| 8 | + """Computer intersection over union. |
| 9 | +
|
| 10 | + Parameters |
| 11 | + ---------- |
| 12 | + bbox : ndarray |
| 13 | + A bounding box in format `(top left x, top left y, width, height)`. |
| 14 | + candidates : ndarray |
| 15 | + A matrix of candidate bounding boxes (one per row) in the same format |
| 16 | + as `bbox`. |
| 17 | +
|
| 18 | + Returns |
| 19 | + ------- |
| 20 | + ndarray |
| 21 | + The intersection over union in [0, 1] between the `bbox` and each |
| 22 | + candidate. A higher score means a larger fraction of the `bbox` is |
| 23 | + occluded by the candidate. |
| 24 | +
|
| 25 | + """ |
| 26 | + bbox_tl, bbox_br = bbox[:2], bbox[:2] + bbox[2:] |
| 27 | + candidates_tl = candidates[:, :2] |
| 28 | + candidates_br = candidates[:, :2] + candidates[:, 2:] |
| 29 | + |
| 30 | + tl = np.c_[np.maximum(bbox_tl[0], candidates_tl[:, 0])[:, np.newaxis], |
| 31 | + np.maximum(bbox_tl[1], candidates_tl[:, 1])[:, np.newaxis]] |
| 32 | + br = np.c_[np.minimum(bbox_br[0], candidates_br[:, 0])[:, np.newaxis], |
| 33 | + np.minimum(bbox_br[1], candidates_br[:, 1])[:, np.newaxis]] |
| 34 | + wh = np.maximum(0., br - tl) |
| 35 | + |
| 36 | + area_intersection = wh.prod(axis=1) |
| 37 | + area_bbox = bbox[2:].prod() |
| 38 | + area_candidates = candidates[:, 2:].prod(axis=1) |
| 39 | + return area_intersection / (area_bbox + area_candidates - area_intersection) |
| 40 | + |
| 41 | + |
| 42 | +def iou_cost(tracks, detections, track_indices=None, |
| 43 | + detection_indices=None): |
| 44 | + """An intersection over union distance metric. |
| 45 | +
|
| 46 | + Parameters |
| 47 | + ---------- |
| 48 | + tracks : List[deep_sort.track.Track] |
| 49 | + A list of tracks. |
| 50 | + detections : List[deep_sort.detection.Detection] |
| 51 | + A list of detections. |
| 52 | + track_indices : Optional[List[int]] |
| 53 | + A list of indices to tracks that should be matched. Defaults to |
| 54 | + all `tracks`. |
| 55 | + detection_indices : Optional[List[int]] |
| 56 | + A list of indices to detections that should be matched. Defaults |
| 57 | + to all `detections`. |
| 58 | +
|
| 59 | + Returns |
| 60 | + ------- |
| 61 | + ndarray |
| 62 | + Returns a cost matrix of shape |
| 63 | + len(track_indices), len(detection_indices) where entry (i, j) is |
| 64 | + `1 - iou(tracks[track_indices[i]], detections[detection_indices[j]])`. |
| 65 | +
|
| 66 | + """ |
| 67 | + if track_indices is None: |
| 68 | + track_indices = np.arange(len(tracks)) |
| 69 | + if detection_indices is None: |
| 70 | + detection_indices = np.arange(len(detections)) |
| 71 | + |
| 72 | + cost_matrix = np.zeros((len(track_indices), len(detection_indices))) |
| 73 | + for row, track_idx in enumerate(track_indices): |
| 74 | + if tracks[track_idx].time_since_update > 1: |
| 75 | + cost_matrix[row, :] = linear_assignment.INFTY_COST |
| 76 | + continue |
| 77 | + |
| 78 | + bbox = tracks[track_idx].to_tlwh() |
| 79 | + candidates = np.asarray([detections[i].tlwh for i in detection_indices]) |
| 80 | + cost_matrix[row, :] = 1. - iou(bbox, candidates) |
| 81 | + return cost_matrix |
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