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r""" Conovlutional Hough matching layers """ | |
import torch.nn as nn | |
import torch | |
from .base.correlation import Correlation | |
from .base.geometry import Geometry | |
from .base.chm import CHM4d, CHM6d | |
class CHMLearner(nn.Module): | |
def __init__(self, ktype, feat_dim): | |
super(CHMLearner, self).__init__() | |
# Scale-wise feature transformation | |
self.scales = [0.5, 1, 2] | |
self.conv2ds = nn.ModuleList([nn.Conv2d(feat_dim, feat_dim // 4, kernel_size=3, padding=1, bias=False) for _ in self.scales]) | |
# CHM layers | |
ksz_translation = 5 | |
ksz_scale = 3 | |
self.chm6d = CHM6d(1, 1, ksz_scale, ksz_translation, ktype) | |
self.chm4d = CHM4d(1, 1, ksz_translation, ktype, bias=True) | |
# Activations | |
self.relu = nn.ReLU(inplace=True) | |
self.sigmoid = nn.Sigmoid() | |
self.softplus = nn.Softplus() | |
def forward(self, src_feat, trg_feat): | |
corr = Correlation.build_correlation6d(src_feat, trg_feat, self.scales, self.conv2ds).unsqueeze(1) | |
bsz, ch, s, s, h, w, h, w = corr.size() | |
# CHM layer (6D) | |
corr = self.chm6d(corr) | |
corr = self.sigmoid(corr) | |
# Scale-space maxpool | |
corr = corr.view(bsz, -1, h, w, h, w).max(dim=1)[0] | |
corr = Geometry.interpolate4d(corr, [h * 2, w * 2]).unsqueeze(1) | |
# CHM layer (4D) | |
corr = self.chm4d(corr).squeeze(1) | |
# To ensure non-negative vote scores & soft cyclic constraints | |
corr = self.softplus(corr) | |
corr = Correlation.mutual_nn_filter(corr.view(bsz, corr.size(-1) ** 2, corr.size(-1) ** 2).contiguous()) | |
return corr | |