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65 lines
2.2 KiB
65 lines
2.2 KiB
3 days ago
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# Copied from https://github.com/mlcommons/training/blob/637c82f9e699cd6caf108f92efb2c1d446b630e0/single_stage_detector/ssd/model/boxes.py
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import torch
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from torch import Tensor
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from typing import Tuple
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def _upcast(t: Tensor) -> Tensor:
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# Protects from numerical overflows in multiplications by upcasting to the equivalent higher type
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if t.is_floating_point():
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return t if t.dtype in (torch.float32, torch.float64) else t.float()
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else:
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return t if t.dtype in (torch.int32, torch.int64) else t.int()
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def box_area(boxes: Tensor) -> Tensor:
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"""
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Computes the area of a set of bounding boxes, which are specified by their
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(x1, y1, x2, y2) coordinates.
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Args:
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boxes (Tensor[N, 4]): boxes for which the area will be computed. They
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are expected to be in (x1, y1, x2, y2) format with
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``0 <= x1 < x2`` and ``0 <= y1 < y2``.
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Returns:
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Tensor[N]: the area for each box
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"""
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boxes = _upcast(boxes)
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return (boxes[:, 2] - boxes[:, 0]) * (boxes[:, 3] - boxes[:, 1])
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# implementation from https://github.com/kuangliu/torchcv/blob/master/torchcv/utils/box.py
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# with slight modifications
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def _box_inter_union(boxes1: Tensor, boxes2: Tensor) -> Tuple[Tensor, Tensor]:
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area1 = box_area(boxes1)
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area2 = box_area(boxes2)
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lt = torch.max(boxes1[:, None, :2], boxes2[:, :2]) # [N,M,2]
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rb = torch.min(boxes1[:, None, 2:], boxes2[:, 2:]) # [N,M,2]
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wh = _upcast(rb - lt).clamp(min=0) # [N,M,2]
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inter = wh[:, :, 0] * wh[:, :, 1] # [N,M]
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union = area1[:, None] + area2 - inter
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return inter, union
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def box_iou(boxes1: Tensor, boxes2: Tensor) -> Tensor:
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"""
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Return intersection-over-union (Jaccard index) between two sets of boxes.
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Both sets of boxes are expected to be in ``(x1, y1, x2, y2)`` format with
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``0 <= x1 < x2`` and ``0 <= y1 < y2``.
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Args:
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boxes1 (Tensor[N, 4]): first set of boxes
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boxes2 (Tensor[M, 4]): second set of boxes
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Returns:
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Tensor[N, M]: the NxM matrix containing the pairwise IoU values for every element in boxes1 and boxes2
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"""
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inter, union = _box_inter_union(boxes1, boxes2)
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iou = inter / union
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return iou
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