Discrepancy in input output format

[YannLepoittevin]

Hi,

First of all, thanks for the nice package.

It seems there is a discrepancy in the input / output format where input is expected as [left, top, right, bottom] as per lines:

bytetrack-pip/bytetracker/byte_tracker.py

Line 215 in 61a06fe

xywh = xyxy2ltwh(xyxys)

and comment:

bytetrack-pip/bytetracker/byte_tracker.py

Line 33 in 61a06fe

# Convert nx4 boxes from [x1, y1, x2, y2] to [x, y, w, h] where xy1=top-left, xy2=bottom-right

But outputs are send back as [center left, center top, right, bottom] as per line:

bytetrack-pip/bytetracker/byte_tracker.py

Line 372 in 61a06fe

xyxy = xywh2xyxy(tlwh)

and definition of:

bytetrack-pip/bytetracker/byte_tracker.py

Line 7 in 61a06fe

def xywh2xyxy(x):

Steps to reproduce:

import numpy as np
from bytetracker import BYTETracker

h, w, n = 480, 640, 10
boxes = np.hstack([np.random.randint(0, w, n)[..., np.newaxis],
                   np.random.randint(0, h, n)[..., np.newaxis],
                   np.random.randint(0, w, n)[..., np.newaxis],
                   np.random.randint(0, h, n)[..., np.newaxis]])
scores = 0.8 + 0.2 * np.random.random(n)[..., np.newaxis]
classes = np.zeros((n, 1))
dets = np.hstack([boxes, scores, classes])

tracker = BYTETracker()
online_targets = tracker.update(dets)

np.allclose(boxes, online_targets[:, :4])

results in >> False with the actual code.

Potential fix, if [left, top, right, bottom] is the way to go with:

def xywh2xyxy(x):
    # Convert nx4 boxes from [x, y, w, h] to [x1, y1, x2, y2] where xy1=top-left, xy2=bottom-right
    try:
        y = x.clone()
    except:
        y = np.copy(x)
    y[:, 0] = x[:, 0]   # top left x
    y[:, 1] = x[:, 1]   # top left y
    y[:, 2] = x[:, 0] + x[:, 2]  # bottom right x
    y[:, 3] = x[:, 1] + x[:, 3]  # bottom right y
    return y

Again, thanks for the package.