def topk_score(scores, K=40):
r"""
get top point in score map.
Args:
scores (Tensor): scores map.
K (int): top K in scores map.
"""
batch, channel, height, width = scores.shape
# get topk score and its index in every H x W(channel dim) feature map
topk_scores, topk_inds = torch.topk(scores.reshape(batch, channel, -1),
K)
topk_inds = topk_inds % (height * width)
topk_ys = (topk_inds / width).int().float()
topk_xs = (topk_inds % width).int().float()
# get all topk in in a batch
topk_score, index = torch.topk(topk_scores.reshape(batch, -1), K)
# div by K because index is grouped by K(C x K shape)
topk_clses = (index / K).int()
topk_inds = gather_feature(topk_inds.view(batch, -1, 1),
index).reshape(batch, K)
topk_ys = gather_feature(topk_ys.reshape(batch, -1, 1),
index).reshape(batch, K)
topk_xs = gather_feature(topk_xs.reshape(batch, -1, 1),
index).reshape(batch, K)
return topk_score, topk_inds, topk_clses, topk_ys, topk_xs
def forward(self, output, mask, index, target):
pred = gather_feature(output, index, use_transform=True)
mask = mask.unsqueeze(dim=2).expand_as(pred).float()
# loss = F.l1_loss(pred * mask, target * mask, reduction='elementwise_mean')
loss = F.l1_loss(pred * mask, target * mask, reduction='sum')
loss = loss / (mask.sum() + 1e-4)
return loss
def decode(fmap, wh, reg=None, cat_spec_wh=False, K=100):
r"""
decode feature maps, width height, regression to detections results.
Args:
fmap (Tensor): input feature map.
wh (Tensor): tensor represents (width, height).
reg (Tensor): tensor represents regression.
cat_spec_wh (bool): whether reshape wh tensor.
K (int): top k value in score map.
"""
batch, channel, height, width = fmap.shape
fmap = CenterNetDecoder.pseudo_nms(fmap)
scores, index, clses, ys, xs = CenterNetDecoder.topk_score(fmap, K=K)
if reg is not None:
reg = gather_feature(reg, index, use_transform=True)
reg = reg.reshape(batch, K, 2)
xs = xs.view(batch, K, 1) + reg[:, :, 0:1]
ys = ys.view(batch, K, 1) + reg[:, :, 1:2]
else:
xs = xs.view(batch, K, 1) + 0.5
ys = ys.view(batch, K, 1) + 0.5
wh = gather_feature(wh, index, use_transform=True)
if cat_spec_wh:
wh = wh.view(batch, K, channel, 2)
clses_ind = clses.view(batch, K, 1, 1).expand(batch, K, 1,
2).long()
wh = wh.gather(2, clses_ind).reshape(batch, K, 2)
else:
wh = wh.reshape(batch, K, 2)
clses = clses.reshape(batch, K, 1).float()
scores = scores.reshape(batch, K, 1)
half_w = wh[..., 0:1] / 2
half_h = wh[..., 1:2] / 2
bboxes = torch.cat(
[xs - half_w, ys - half_h, xs + half_w, ys + half_h], dim=2)
detections = (bboxes, scores, clses)
return detections
