# mmcv.ops.bbox 源代码

```# Copyright (c) OpenMMLab. All rights reserved.

[文档]def bbox_overlaps(bboxes1, bboxes2, mode='iou', aligned=False, offset=0):
"""Calculate overlap between two set of bboxes.

If ``aligned`` is ``False``, then calculate the ious between each bbox
of bboxes1 and bboxes2, otherwise the ious between each aligned pair of
bboxes1 and bboxes2.

Args:
bboxes1 (Tensor): shape (m, 4) in <x1, y1, x2, y2> format or empty.
bboxes2 (Tensor): shape (n, 4) in <x1, y1, x2, y2> format or empty.
If aligned is ``True``, then m and n must be equal.
mode (str): "iou" (intersection over union) or iof (intersection over
foreground).

Returns:
ious(Tensor): shape (m, n) if aligned == False else shape (m, 1)

Example:
>>> bboxes1 = torch.FloatTensor([
>>>     [0, 0, 10, 10],
>>>     [10, 10, 20, 20],
>>>     [32, 32, 38, 42],
>>> ])
>>> bboxes2 = torch.FloatTensor([
>>>     [0, 0, 10, 20],
>>>     [0, 10, 10, 19],
>>>     [10, 10, 20, 20],
>>> ])
>>> bbox_overlaps(bboxes1, bboxes2)
tensor([[0.5000, 0.0000, 0.0000],
[0.0000, 0.0000, 1.0000],
[0.0000, 0.0000, 0.0000]])

Example:
>>> empty = torch.FloatTensor([])
>>> nonempty = torch.FloatTensor([
>>>     [0, 0, 10, 9],
>>> ])
>>> assert tuple(bbox_overlaps(empty, nonempty).shape) == (0, 1)
>>> assert tuple(bbox_overlaps(nonempty, empty).shape) == (1, 0)
>>> assert tuple(bbox_overlaps(empty, empty).shape) == (0, 0)
"""

mode_dict = {'iou': 0, 'iof': 1}
assert mode in mode_dict.keys()
mode_flag = mode_dict[mode]
# Either the boxes are empty or the length of boxes' last dimension is 4
assert (bboxes1.size(-1) == 4 or bboxes1.size(0) == 0)
assert (bboxes2.size(-1) == 4 or bboxes2.size(0) == 0)
assert offset == 1 or offset == 0

rows = bboxes1.size(0)
cols = bboxes2.size(0)
if aligned:
assert rows == cols

if rows * cols == 0:
return bboxes1.new(rows, 1) if aligned else bboxes1.new(rows, cols)

if aligned:
ious = bboxes1.new_zeros(rows)
else:
ious = bboxes1.new_zeros((rows, cols))
ext_module.bbox_overlaps(
bboxes1, bboxes2, ious, mode=mode_flag, aligned=aligned, offset=offset)
return ious
```