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""" | ||
SORT: A Simple, Online and Realtime Tracker | ||
Copyright (C) 2016-2020 Alex Bewley [email protected] | ||
This program is free software: you can redistribute it and/or modify | ||
it under the terms of the GNU General Public License as published by | ||
the Free Software Foundation, either version 3 of the License, or | ||
(at your option) any later version. | ||
This program is distributed in the hope that it will be useful, | ||
but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
GNU General Public License for more details. | ||
You should have received a copy of the GNU General Public License | ||
along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
""" | ||
from __future__ import print_function | ||
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import os | ||
import numpy as np | ||
import matplotlib | ||
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matplotlib.use('TkAgg') | ||
import matplotlib.pyplot as plt | ||
import matplotlib.patches as patches | ||
from skimage import io | ||
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import glob | ||
import time | ||
import argparse | ||
from filterpy.kalman import KalmanFilter | ||
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np.random.seed(0) | ||
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def linear_assignment(cost_matrix): | ||
try: | ||
import lap | ||
_, x, y = lap.lapjv(cost_matrix, extend_cost=True) | ||
return np.array([[y[i], i] for i in x if i >= 0]) # | ||
except ImportError: | ||
from scipy.optimize import linear_sum_assignment | ||
x, y = linear_sum_assignment(cost_matrix) | ||
return np.array(list(zip(x, y))) | ||
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def iou_batch(bb_test, bb_gt): | ||
""" | ||
From SORT: Computes IOU between two bboxes in the form [x1,y1,x2,y2] | ||
""" | ||
bb_gt = np.expand_dims(bb_gt, 0) | ||
bb_test = np.expand_dims(bb_test, 1) | ||
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xx1 = np.maximum(bb_test[..., 0], bb_gt[..., 0]) | ||
yy1 = np.maximum(bb_test[..., 1], bb_gt[..., 1]) | ||
xx2 = np.minimum(bb_test[..., 2], bb_gt[..., 2]) | ||
yy2 = np.minimum(bb_test[..., 3], bb_gt[..., 3]) | ||
w = np.maximum(0., xx2 - xx1) | ||
h = np.maximum(0., yy2 - yy1) | ||
wh = w * h | ||
o = wh / ((bb_test[..., 2] - bb_test[..., 0]) * (bb_test[..., 3] - bb_test[..., 1]) | ||
+ (bb_gt[..., 2] - bb_gt[..., 0]) * (bb_gt[..., 3] - bb_gt[..., 1]) - wh) | ||
return (o) | ||
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def convert_bbox_to_z(bbox): | ||
""" | ||
Takes a bounding box in the form [x1,y1,x2,y2] and returns z in the form | ||
[x,y,s,r] where x,y is the centre of the box and s is the scale/area and r is | ||
the aspect ratio | ||
""" | ||
w = bbox[2] - bbox[0] | ||
h = bbox[3] - bbox[1] | ||
x = bbox[0] + w / 2. | ||
y = bbox[1] + h / 2. | ||
s = w * h # scale is just area | ||
r = w / float(h) | ||
return np.array([x, y, s, r]).reshape((4, 1)) | ||
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def convert_x_to_bbox(x, score=None): | ||
""" | ||
Takes a bounding box in the centre form [x,y,s,r] and returns it in the form | ||
[x1,y1,x2,y2] where x1,y1 is the top left and x2,y2 is the bottom right | ||
""" | ||
w = np.sqrt(x[2] * x[3]) | ||
h = x[2] / w | ||
if (score == None): | ||
return np.array([x[0] - w / 2., x[1] - h / 2., x[0] + w / 2., x[1] + h / 2.]).reshape((1, 4)) | ||
else: | ||
return np.array([x[0] - w / 2., x[1] - h / 2., x[0] + w / 2., x[1] + h / 2., score]).reshape((1, 5)) | ||
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class KalmanBoxTracker(object): | ||
""" | ||
This class represents the internal state of individual tracked objects observed as bbox. | ||
""" | ||
count = 0 | ||
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def __init__(self, bbox): | ||
""" | ||
Initialises a tracker using initial bounding box. | ||
""" | ||
# define constant velocity model | ||
self.kf = KalmanFilter(dim_x=7, dim_z=4) | ||
self.kf.F = np.array( | ||
[[1, 0, 0, 0, 1, 0, 0], [0, 1, 0, 0, 0, 1, 0], [0, 0, 1, 0, 0, 0, 1], [0, 0, 0, 1, 0, 0, 0], | ||
[0, 0, 0, 0, 1, 0, 0], [0, 0, 0, 0, 0, 1, 0], [0, 0, 0, 0, 0, 0, 1]]) | ||
self.kf.H = np.array( | ||
[[1, 0, 0, 0, 0, 0, 0], [0, 1, 0, 0, 0, 0, 0], [0, 0, 1, 0, 0, 0, 0], [0, 0, 0, 1, 0, 0, 0]]) | ||
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self.kf.R[2:, 2:] *= 10. | ||
self.kf.P[4:, 4:] *= 1000. # give high uncertainty to the unobservable initial velocities | ||
self.kf.P *= 10. | ||
self.kf.Q[-1, -1] *= 0.01 | ||
self.kf.Q[4:, 4:] *= 0.01 | ||
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self.kf.x[:4] = convert_bbox_to_z(bbox) | ||
self.time_since_update = 0 | ||
self.id = KalmanBoxTracker.count | ||
KalmanBoxTracker.count += 1 | ||
self.history = [] | ||
self.hits = 0 | ||
self.hit_streak = 0 | ||
self.age = 0 | ||
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def update(self, bbox): | ||
""" | ||
Updates the state vector with observed bbox. | ||
""" | ||
self.time_since_update = 0 | ||
self.history = [] | ||
self.hits += 1 | ||
self.hit_streak += 1 | ||
self.kf.update(convert_bbox_to_z(bbox)) | ||
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def predict(self): | ||
""" | ||
Advances the state vector and returns the predicted bounding box estimate. | ||
""" | ||
if ((self.kf.x[6] + self.kf.x[2]) <= 0): | ||
self.kf.x[6] *= 0.0 | ||
self.kf.predict() | ||
self.age += 1 | ||
if (self.time_since_update > 0): | ||
self.hit_streak = 0 | ||
self.time_since_update += 1 | ||
self.history.append(convert_x_to_bbox(self.kf.x)) | ||
return self.history[-1] | ||
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def get_state(self): | ||
""" | ||
Returns the current bounding box estimate. | ||
""" | ||
return convert_x_to_bbox(self.kf.x) | ||
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def associate_detections_to_trackers(detections, trackers, iou_threshold=0.3): | ||
""" | ||
Assigns detections to tracked object (both represented as bounding boxes) | ||
Returns 3 lists of matches, unmatched_detections and unmatched_trackers | ||
""" | ||
if (len(trackers) == 0): | ||
return np.empty((0, 2), dtype=int), np.arange(len(detections)), np.empty((0, 5), dtype=int) | ||
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iou_matrix = iou_batch(detections, trackers) | ||
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if min(iou_matrix.shape) > 0: | ||
a = (iou_matrix > iou_threshold).astype(np.int32) | ||
if a.sum(1).max() == 1 and a.sum(0).max() == 1: | ||
matched_indices = np.stack(np.where(a), axis=1) | ||
else: | ||
matched_indices = linear_assignment(-iou_matrix) | ||
else: | ||
matched_indices = np.empty(shape=(0, 2)) | ||
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unmatched_detections = [] | ||
for d, det in enumerate(detections): | ||
if (d not in matched_indices[:, 0]): | ||
unmatched_detections.append(d) | ||
unmatched_trackers = [] | ||
for t, trk in enumerate(trackers): | ||
if (t not in matched_indices[:, 1]): | ||
unmatched_trackers.append(t) | ||
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# filter out matched with low IOU | ||
matches = [] | ||
for m in matched_indices: | ||
if (iou_matrix[m[0], m[1]] < iou_threshold): | ||
unmatched_detections.append(m[0]) | ||
unmatched_trackers.append(m[1]) | ||
else: | ||
matches.append(m.reshape(1, 2)) | ||
if (len(matches) == 0): | ||
matches = np.empty((0, 2), dtype=int) | ||
else: | ||
matches = np.concatenate(matches, axis=0) | ||
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return matches, np.array(unmatched_detections), np.array(unmatched_trackers) | ||
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class Sort(object): | ||
def __init__(self, max_age=1, min_hits=3, iou_threshold=0.3): | ||
""" | ||
Sets key parameters for SORT | ||
""" | ||
self.max_age = max_age | ||
self.min_hits = min_hits | ||
self.iou_threshold = iou_threshold | ||
self.trackers = [] | ||
self.frame_count = 0 | ||
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def update(self, dets=np.empty((0, 5))): | ||
""" | ||
Params: | ||
dets - a numpy array of detections in the format [[x1,y1,x2,y2,score],[x1,y1,x2,y2,score],...] | ||
Requires: this method must be called once for each frame even with empty detections (use np.empty((0, 5)) for frames without detections). | ||
Returns the a similar array, where the last column is the object ID. | ||
NOTE: The number of objects returned may differ from the number of detections provided. | ||
""" | ||
self.frame_count += 1 | ||
# get predicted locations from existing trackers. | ||
trks = np.zeros((len(self.trackers), 5)) | ||
to_del = [] | ||
ret = [] | ||
for t, trk in enumerate(trks): | ||
pos = self.trackers[t].predict()[0] | ||
trk[:] = [pos[0], pos[1], pos[2], pos[3], 0] | ||
if np.any(np.isnan(pos)): | ||
to_del.append(t) | ||
trks = np.ma.compress_rows(np.ma.masked_invalid(trks)) | ||
for t in reversed(to_del): | ||
self.trackers.pop(t) | ||
matched, unmatched_dets, unmatched_trks = associate_detections_to_trackers(dets, trks, self.iou_threshold) | ||
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# update matched trackers with assigned detections | ||
for m in matched: | ||
self.trackers[m[1]].update(dets[m[0], :]) | ||
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# create and initialise new trackers for unmatched detections | ||
for i in unmatched_dets: | ||
trk = KalmanBoxTracker(dets[i, :]) | ||
self.trackers.append(trk) | ||
i = len(self.trackers) | ||
for trk in reversed(self.trackers): | ||
d = trk.get_state()[0] | ||
if (trk.time_since_update < 1) and (trk.hit_streak >= self.min_hits or self.frame_count <= self.min_hits): | ||
ret.append(np.concatenate((d, [trk.id + 1])).reshape(1, -1)) # +1 as MOT benchmark requires positive | ||
i -= 1 | ||
# remove dead tracklet | ||
if (trk.time_since_update > self.max_age): | ||
self.trackers.pop(i) | ||
if (len(ret) > 0): | ||
return np.concatenate(ret) | ||
return np.empty((0, 5)) | ||
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def parse_args(): | ||
"""Parse input arguments.""" | ||
parser = argparse.ArgumentParser(description='SORT demo') | ||
parser.add_argument('--display', dest='display', help='Display online tracker output (slow) [False]', | ||
action='store_true') | ||
parser.add_argument("--seq_path", help="Path to detections.", type=str, default='data') | ||
parser.add_argument("--phase", help="Subdirectory in seq_path.", type=str, default='train') | ||
parser.add_argument("--max_age", | ||
help="Maximum number of frames to keep alive a track without associated detections.", | ||
type=int, default=1) | ||
parser.add_argument("--min_hits", | ||
help="Minimum number of associated detections before track is initialised.", | ||
type=int, default=3) | ||
parser.add_argument("--iou_threshold", help="Minimum IOU for match.", type=float, default=0.3) | ||
args = parser.parse_args() | ||
return args | ||
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if __name__ == '__main__': | ||
# all train | ||
args = parse_args() | ||
display = args.display | ||
phase = args.phase | ||
total_time = 0.0 | ||
total_frames = 0 | ||
colours = np.random.rand(32, 3) # used only for display | ||
if (display): | ||
if not os.path.exists('mot_benchmark'): | ||
print( | ||
'\n\tERROR: mot_benchmark link not found!\n\n Create a symbolic link to the MOT benchmark\n (https://motchallenge.net/data/2D_MOT_2015/#download). E.g.:\n\n $ ln -s /path/to/MOT2015_challenge/2DMOT2015 mot_benchmark\n\n') | ||
exit() | ||
plt.ion() | ||
fig = plt.figure() | ||
ax1 = fig.add_subplot(111, aspect='equal') | ||
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if not os.path.exists('output'): | ||
os.makedirs('output') | ||
pattern = os.path.join(args.seq_path, phase, '*', 'det', 'det.txt') | ||
for seq_dets_fn in glob.glob(pattern): | ||
mot_tracker = Sort(max_age=args.max_age, | ||
min_hits=args.min_hits, | ||
iou_threshold=args.iou_threshold) # create instance of the SORT tracker | ||
seq_dets = np.loadtxt(seq_dets_fn, delimiter=',') | ||
seq = seq_dets_fn[pattern.find('*'):].split(os.path.sep)[0] | ||
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with open(os.path.join('output', '%s.txt' % (seq)), 'w') as out_file: | ||
print("Processing %s." % (seq)) | ||
for frame in range(int(seq_dets[:, 0].max())): | ||
frame += 1 # detection and frame numbers begin at 1 | ||
dets = seq_dets[seq_dets[:, 0] == frame, 2:7] | ||
dets[:, 2:4] += dets[:, 0:2] # convert to [x1,y1,w,h] to [x1,y1,x2,y2] | ||
total_frames += 1 | ||
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if (display): | ||
fn = os.path.join('mot_benchmark', phase, seq, 'img1', '%06d.jpg' % (frame)) | ||
im = io.imread(fn) | ||
ax1.imshow(im) | ||
plt.title(seq + ' Tracked Targets') | ||
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start_time = time.time() | ||
trackers = mot_tracker.update(dets) | ||
cycle_time = time.time() - start_time | ||
total_time += cycle_time | ||
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for d in trackers: | ||
print('%d,%d,%.2f,%.2f,%.2f,%.2f,1,-1,-1,-1' % (frame, d[4], d[0], d[1], d[2] - d[0], d[3] - d[1]), | ||
file=out_file) | ||
if (display): | ||
d = d.astype(np.int32) | ||
ax1.add_patch(patches.Rectangle((d[0], d[1]), d[2] - d[0], d[3] - d[1], fill=False, lw=3, | ||
ec=colours[d[4] % 32, :])) | ||
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if (display): | ||
fig.canvas.flush_events() | ||
plt.draw() | ||
ax1.cla() | ||
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print("Total Tracking took: %.3f seconds for %d frames or %.1f FPS" % ( | ||
total_time, total_frames, total_frames / total_time)) | ||
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if (display): | ||
print("Note: to get real runtime results run without the option: --display") |