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# Copyright 2019-present NAVER Corp.
# CC BY-NC-SA 3.0
# Available only for non-commercial use
import pdb
import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
""" Different samplers, each specifying how to sample pixels for the AP loss.
"""
class FullSampler(nn.Module):
""" all pixels are selected
- feats: keypoint descriptors
- confs: reliability values
"""
def __init__(self):
nn.Module.__init__(self)
self.mode = 'bilinear'
self.padding = 'zeros'
@staticmethod
def _aflow_to_grid(aflow):
H, W = aflow.shape[2:]
grid = aflow.permute(0,2,3,1).clone()
grid[:,:,:,0] *= 2/(W-1)
grid[:,:,:,1] *= 2/(H-1)
grid -= 1
grid[torch.isnan(grid)] = 9e9 # invalids
return grid
def _warp(self, feats, confs, aflow):
if isinstance(aflow, tuple): return aflow # result was precomputed
feat1, feat2 = feats
conf1, conf2 = confs if confs else (None,None)
B, two, H, W = aflow.shape
D = feat1.shape[1]
assert feat1.shape == feat2.shape == (B, D, H, W) # D = 128, B = batch
assert conf1.shape == conf2.shape == (B, 1, H, W) if confs else True
# warp img2 to img1
grid = self._aflow_to_grid(aflow)
ones2 = feat2.new_ones(feat2[:,0:1].shape)
feat2to1 = F.grid_sample(feat2, grid, mode=self.mode, padding_mode=self.padding)
mask2to1 = F.grid_sample(ones2, grid, mode='nearest', padding_mode='zeros')
conf2to1 = F.grid_sample(conf2, grid, mode=self.mode, padding_mode=self.padding) \
if confs else None
return feat2to1, mask2to1.byte(), conf2to1
def _warp_positions(self, aflow):
B, two, H, W = aflow.shape
assert two == 2
Y = torch.arange(H, device=aflow.device)
X = torch.arange(W, device=aflow.device)
XY = torch.stack(torch.meshgrid(Y,X)[::-1], dim=0)
XY = XY[None].expand(B, 2, H, W).float()
grid = self._aflow_to_grid(aflow)
XY2 = F.grid_sample(XY, grid, mode='bilinear', padding_mode='zeros')
return XY, XY2
class SubSampler (FullSampler):
""" pixels are selected in an uniformly spaced grid
"""
def __init__(self, border, subq, subd, perimage=False):
FullSampler.__init__(self)
assert subq % subd == 0, 'subq must be multiple of subd'
self.sub_q = subq
self.sub_d = subd
self.border = border
self.perimage = perimage
def __repr__(self):
return "SubSampler(border=%d, subq=%d, subd=%d, perimage=%d)" % (
self.border, self.sub_q, self.sub_d, self.perimage)
def __call__(self, feats, confs, aflow):
feat1, conf1 = feats[0], (confs[0] if confs else None)
# warp with optical flow in img1 coords
feat2, mask2, conf2 = self._warp(feats, confs, aflow)
# subsample img1
slq = slice(self.border, -self.border or None, self.sub_q)
feat1 = feat1[:, :, slq, slq]
conf1 = conf1[:, :, slq, slq] if confs else None
# subsample img2
sld = slice(self.border, -self.border or None, self.sub_d)
feat2 = feat2[:, :, sld, sld]
mask2 = mask2[:, :, sld, sld]
conf2 = conf2[:, :, sld, sld] if confs else None
B, D, Hq, Wq = feat1.shape
B, D, Hd, Wd = feat2.shape
# compute gt
if self.perimage or self.sub_q != self.sub_d:
# compute ground-truth by comparing pixel indices
f = feats[0][0:1,0] if self.perimage else feats[0][:,0]
idxs = torch.arange(f.numel(), dtype=torch.int64, device=feat1.device).view(f.shape)
idxs1 = idxs[:, slq, slq].reshape(-1,Hq*Wq)
idxs2 = idxs[:, sld, sld].reshape(-1,Hd*Wd)
if self.perimage:
gt = (idxs1[0].view(-1,1) == idxs2[0].view(1,-1))
gt = gt[None,:,:].expand(B, Hq*Wq, Hd*Wd)
else :
gt = (idxs1.view(-1,1) == idxs2.view(1,-1))
else:
gt = torch.eye(feat1[:,0].numel(), dtype=torch.uint8, device=feat1.device) # always binary for AP loss
# compute all images together
queries = feat1.reshape(B,D,-1) # B x D x (Hq x Wq)
database = feat2.reshape(B,D,-1) # B x D x (Hd x Wd)
if self.perimage:
queries = queries.transpose(1,2) # B x (Hd x Wd) x D
scores = torch.bmm(queries, database) # B x (Hq x Wq) x (Hd x Wd)
else:
queries = queries .transpose(1,2).reshape(-1,D) # (B x Hq x Wq) x D
database = database.transpose(1,0).reshape(D,-1) # D x (B x Hd x Wd)
scores = torch.matmul(queries, database) # (B x Hq x Wq) x (B x Hd x Wd)
# compute reliability
qconf = (conf1 + conf2)/2 if confs else None
assert gt.shape == scores.shape
return scores, gt, mask2, qconf
class NghSampler (FullSampler):
""" all pixels in a small neighborhood
"""
def __init__(self, ngh, subq=1, subd=1, ignore=1, border=None):
FullSampler.__init__(self)
assert 0 <= ignore < ngh
self.ngh = ngh
self.ignore = ignore
assert subd <= ngh
self.sub_q = subq
self.sub_d = subd
if border is None: border = ngh
assert border >= ngh, 'border has to be larger than ngh'
self.border = border
def __repr__(self):
return "NghSampler(ngh=%d, subq=%d, subd=%d, ignore=%d, border=%d)" % (
self.ngh, self.sub_q, self.sub_d, self.ignore, self.border)
def trans(self, arr, i, j):
s = lambda i: slice(self.border+i, i-self.border or None, self.sub_q)
return arr[:,:,s(j),s(i)]
def __call__(self, feats, confs, aflow):
feat1, conf1 = feats[0], (confs[0] if confs else None)
# warp with optical flow in img1 coords
feat2, mask2, conf2 = self._warp(feats, confs, aflow)
qfeat = self.trans(feat1,0,0)
qconf = (self.trans(conf1,0,0) + self.trans(conf2,0,0)) / 2 if confs else None
mask2 = self.trans(mask2,0,0)
scores_at = lambda i,j: (qfeat * self.trans(feat2,i,j)).sum(dim=1)
# compute scores for all neighbors
B, D = feat1.shape[:2]
min_d = self.ignore**2
max_d = self.ngh**2
rad = (self.ngh//self.sub_d) * self.ngh # make an integer multiple
negs = []
offsets = []
for j in range(-rad, rad+1, self.sub_d):
for i in range(-rad, rad+1, self.sub_d):
if not(min_d < i*i + j*j <= max_d):
continue # out of scope
offsets.append((i,j)) # Note: this list is just for debug
negs.append( scores_at(i,j) )
scores = torch.stack([scores_at(0,0)] + negs, dim=-1)
gt = scores.new_zeros(scores.shape, dtype=torch.uint8)
gt[..., 0] = 1 # only the center point is positive
return scores, gt, mask2, qconf
class FarNearSampler (FullSampler):
""" Sample pixels from *both* a small neighborhood *and* far-away pixels.
How it works?
1) Queries are sampled from img1,
- at least `border` pixels from borders and
- on a grid with step = `subq`
2) Close database pixels
- from the corresponding image (img2),
- within a `ngh` distance radius
- on a grid with step = `subd_ngh`
- ignored if distance to query is >0 and <=`ignore`
3) Far-away database pixels from ,
- from all batch images in `img2`
- at least `border` pixels from borders
- on a grid with step = `subd_far`
"""
def __init__(self, subq, ngh, subd_ngh, subd_far, border=None, ignore=1,
maxpool_ngh=False ):
FullSampler.__init__(self)
border = border or ngh
assert ignore < ngh < subd_far, 'neighborhood needs to be smaller than far step'
self.close_sampler = NghSampler(ngh=ngh, subq=subq, subd=subd_ngh,
ignore=not(maxpool_ngh), border=border)
self.faraway_sampler = SubSampler(border=border, subq=subq, subd=subd_far)
self.maxpool_ngh = maxpool_ngh
def __repr__(self):
c,f = self.close_sampler, self.faraway_sampler
res = "FarNearSampler(subq=%d, ngh=%d" % (c.sub_q, c.ngh)
res += ", subd_ngh=%d, subd_far=%d" % (c.sub_d, f.sub_d)
res += ", border=%d, ign=%d" % (f.border, c.ignore)
res += ", maxpool_ngh=%d" % self.maxpool_ngh
return res+')'
def __call__(self, feats, confs, aflow):
# warp with optical flow in img1 coords
aflow = self._warp(feats, confs, aflow)
# sample ngh pixels
scores1, gt1, msk1, conf1 = self.close_sampler(feats, confs, aflow)
scores1, gt1 = scores1.view(-1,scores1.shape[-1]), gt1.view(-1,gt1.shape[-1])
if self.maxpool_ngh:
# we consider all scores from ngh as potential positives
scores1, self._cached_maxpool_ngh = scores1.max(dim=1,keepdim=True)
gt1 = gt1[:, 0:1]
# sample far pixels
scores2, gt2, msk2, conf2 = self.faraway_sampler(feats, confs, aflow)
# assert (msk1 == msk2).all()
# assert (conf1 == conf2).all()
return (torch.cat((scores1,scores2),dim=1),
torch.cat((gt1, gt2), dim=1),
msk1, conf1 if confs else None)
class NghSampler2 (nn.Module):
""" Similar to NghSampler, but doesnt warp the 2nd image.
Distance to GT => 0 ... pos_d ... neg_d ... ngh
Pixel label => + + + + + + 0 0 - - - - - - -
Subsample on query side: if > 0, regular grid
< 0, random points
In both cases, the number of query points is = W*H/subq**2
"""
def __init__(self, ngh, subq=1, subd=1, pos_d=0, neg_d=2, border=None,
maxpool_pos=True, subd_neg=0):
nn.Module.__init__(self)
assert 0 <= pos_d < neg_d <= (ngh if ngh else 99)
self.ngh = ngh
self.pos_d = pos_d
self.neg_d = neg_d
assert subd <= ngh or ngh == 0
assert subq != 0
self.sub_q = subq
self.sub_d = subd
self.sub_d_neg = subd_neg
if border is None: border = ngh
assert border >= ngh, 'border has to be larger than ngh'
self.border = border
self.maxpool_pos = maxpool_pos
self.precompute_offsets()
def precompute_offsets(self):
pos_d2 = self.pos_d**2
neg_d2 = self.neg_d**2
rad2 = self.ngh**2
rad = (self.ngh//self.sub_d) * self.ngh # make an integer multiple
pos = []
neg = []
for j in range(-rad, rad+1, self.sub_d):
for i in range(-rad, rad+1, self.sub_d):
d2 = i*i + j*j
if d2 <= pos_d2:
pos.append( (i,j) )
elif neg_d2 <= d2 <= rad2:
neg.append( (i,j) )
self.register_buffer('pos_offsets', torch.LongTensor(pos).view(-1,2).t())
self.register_buffer('neg_offsets', torch.LongTensor(neg).view(-1,2).t())
def gen_grid(self, step, aflow):
B, two, H, W = aflow.shape
dev = aflow.device
b1 = torch.arange(B, device=dev)
if step > 0:
# regular grid
x1 = torch.arange(self.border, W-self.border, step, device=dev)
y1 = torch.arange(self.border, H-self.border, step, device=dev)
H1, W1 = len(y1), len(x1)
x1 = x1[None,None,:].expand(B,H1,W1).reshape(-1)
y1 = y1[None,:,None].expand(B,H1,W1).reshape(-1)
b1 = b1[:,None,None].expand(B,H1,W1).reshape(-1)
shape = (B, H1, W1)
else:
# randomly spread
n = (H - 2*self.border) * (W - 2*self.border) // step**2
x1 = torch.randint(self.border, W-self.border, (n,), device=dev)
y1 = torch.randint(self.border, H-self.border, (n,), device=dev)
x1 = x1[None,:].expand(B,n).reshape(-1)
y1 = y1[None,:].expand(B,n).reshape(-1)
b1 = b1[:,None].expand(B,n).reshape(-1)
shape = (B, n)
return b1, y1, x1, shape
def forward(self, feats, confs, aflow, **kw):
B, two, H, W = aflow.shape
assert two == 2
feat1, conf1 = feats[0], (confs[0] if confs else None)
feat2, conf2 = feats[1], (confs[1] if confs else None)
# positions in the first image
b1, y1, x1, shape = self.gen_grid(self.sub_q, aflow)
# sample features from first image
feat1 = feat1[b1, :, y1, x1]
qconf = conf1[b1, :, y1, x1].view(shape) if confs else None
#sample GT from second image
b2 = b1
xy2 = (aflow[b1, :, y1, x1] + 0.5).long().t()
mask = (0 <= xy2[0]) * (0 <= xy2[1]) * (xy2[0] < W) * (xy2[1] < H)
mask = mask.view(shape)
def clamp(xy):
torch.clamp(xy[0], 0, W-1, out=xy[0])
torch.clamp(xy[1], 0, H-1, out=xy[1])
return xy
# compute positive scores
xy2p = clamp(xy2[:,None,:] + self.pos_offsets[:,:,None])
pscores = (feat1[None,:,:] * feat2[b2, :, xy2p[1], xy2p[0]]).sum(dim=-1).t()
# xy1p = clamp(torch.stack((x1,y1))[:,None,:] + self.pos_offsets[:,:,None])
# grid = FullSampler._aflow_to_grid(aflow)
# feat2p = F.grid_sample(feat2, grid, mode='bilinear', padding_mode='border')
# pscores = (feat1[None,:,:] * feat2p[b1,:,xy1p[1], xy1p[0]]).sum(dim=-1).t()
if self.maxpool_pos:
pscores, pos = pscores.max(dim=1, keepdim=True)
if confs:
sel = clamp(xy2 + self.pos_offsets[:,pos.view(-1)])
qconf = (qconf + conf2[b2, :, sel[1], sel[0]].view(shape))/2
# compute negative scores
xy2n = clamp(xy2[:,None,:] + self.neg_offsets[:,:,None])
nscores = (feat1[None,:,:] * feat2[b2, :, xy2n[1], xy2n[0]]).sum(dim=-1).t()
if self.sub_d_neg:
# add distractors from a grid
b3, y3, x3, _ = self.gen_grid(self.sub_d_neg, aflow)
distractors = feat2[b3, :, y3, x3]
dscores = torch.matmul(feat1, distractors.t())
del distractors
# remove scores that corresponds to positives or nulls
dis2 = (x3 - xy2[0][:,None])**2 + (y3 - xy2[1][:,None])**2
dis2 += (b3 != b2[:,None]).long() * self.neg_d**2
dscores[dis2 < self.neg_d**2] = 0
scores = torch.cat((pscores, nscores, dscores), dim=1)
else:
# concat everything
scores = torch.cat((pscores, nscores), dim=1)
gt = scores.new_zeros(scores.shape, dtype=torch.uint8)
gt[:, :pscores.shape[1]] = 1
return scores, gt, mask, qconf
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