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import torch
import torch.nn as nn
from einops.einops import rearrange
from .backbone import build_backbone
from .utils.position_encoding import PositionEncodingSine
from .loftr_module import LocalFeatureTransformer, FinePreprocess
from .utils.coarse_matching import CoarseMatching
from .utils.fine_matching import FineMatching
class LoFTR(nn.Module):
def __init__(self, config):
super().__init__()
# Misc
self.config = config
# Modules
self.backbone = build_backbone(config)
self.pos_encoding = PositionEncodingSine(
config['coarse']['d_model'],
temp_bug_fix=config['coarse']['temp_bug_fix'])
self.loftr_coarse = LocalFeatureTransformer(config['coarse'])
self.coarse_matching = CoarseMatching(config['match_coarse'])
self.fine_preprocess = FinePreprocess(config)
self.loftr_fine = LocalFeatureTransformer(config["fine"])
self.fine_matching = FineMatching()
def forward(self, data):
"""
Update:
data (dict): {
'image0': (torch.Tensor): (N, 1, H, W)
'image1': (torch.Tensor): (N, 1, H, W)
'mask0'(optional) : (torch.Tensor): (N, H, W) '0' indicates a padded position
'mask1'(optional) : (torch.Tensor): (N, H, W)
}
"""
# 1. Local Feature CNN
data.update({
'bs': data['image0'].size(0),
'hw0_i': data['image0'].shape[2:], 'hw1_i': data['image1'].shape[2:]
})
if data['hw0_i'] == data['hw1_i']: # faster & better BN convergence
feats_c, feats_f = self.backbone(torch.cat([data['image0'], data['image1']], dim=0))
(feat_c0, feat_c1), (feat_f0, feat_f1) = feats_c.split(data['bs']), feats_f.split(data['bs'])
else: # handle different input shapes
(feat_c0, feat_f0), (feat_c1, feat_f1) = self.backbone(data['image0']), self.backbone(data['image1'])
data.update({
'hw0_c': feat_c0.shape[2:], 'hw1_c': feat_c1.shape[2:],
'hw0_f': feat_f0.shape[2:], 'hw1_f': feat_f1.shape[2:]
})
# 2. coarse-level loftr module
# add featmap with positional encoding, then flatten it to sequence [N, HW, C]
feat_c0 = rearrange(self.pos_encoding(feat_c0), 'n c h w -> n (h w) c')
feat_c1 = rearrange(self.pos_encoding(feat_c1), 'n c h w -> n (h w) c')
mask_c0 = mask_c1 = None # mask is useful in training
if 'mask0' in data:
mask_c0, mask_c1 = data['mask0'].flatten(-2), data['mask1'].flatten(-2)
feat_c0, feat_c1 = self.loftr_coarse(feat_c0, feat_c1, mask_c0, mask_c1)
# 3. match coarse-level
self.coarse_matching(feat_c0, feat_c1, data, mask_c0=mask_c0, mask_c1=mask_c1)
# 4. fine-level refinement
feat_f0_unfold, feat_f1_unfold = self.fine_preprocess(feat_f0, feat_f1, feat_c0, feat_c1, data)
if feat_f0_unfold.size(0) != 0: # at least one coarse level predicted
feat_f0_unfold, feat_f1_unfold = self.loftr_fine(feat_f0_unfold, feat_f1_unfold)
# 5. match fine-level
self.fine_matching(feat_f0_unfold, feat_f1_unfold, data)
def load_state_dict(self, state_dict, *args, **kwargs):
for k in list(state_dict.keys()):
if k.startswith('matcher.'):
state_dict[k.replace('matcher.', '', 1)] = state_dict.pop(k)
return super().load_state_dict(state_dict, *args, **kwargs)
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