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import torch
import torch.nn as nn
import torch.nn.init as init
import torch.nn.functional as F
def initialize_weights(net_l, scale=1):
if not isinstance(net_l, list):
net_l = [net_l]
for net in net_l:
for m in net.modules():
if isinstance(m, nn.Conv2d):
init.kaiming_normal_(m.weight, a=0, mode='fan_in')
m.weight.data *= scale # for residual block
if m.bias is not None:
m.bias.data.zero_()
elif isinstance(m, nn.Linear):
init.kaiming_normal_(m.weight, a=0, mode='fan_in')
m.weight.data *= scale
if m.bias is not None:
m.bias.data.zero_()
elif isinstance(m, nn.BatchNorm2d):
init.constant_(m.weight, 1)
init.constant_(m.bias.data, 0.0)
def make_layer(block, n_layers):
layers = []
for _ in range(n_layers):
layers.append(block())
return nn.Sequential(*layers)
class ResidualBlock_noBN(nn.Module):
'''Residual block w/o BN
---Conv-ReLU-Conv-+-
|________________|
'''
def __init__(self, nf=64):
super(ResidualBlock_noBN, self).__init__()
self.conv1 = nn.Conv2d(nf, nf, 3, 1, 1, bias=True)
self.conv2 = nn.Conv2d(nf, nf, 3, 1, 1, bias=True)
# initialization
initialize_weights([self.conv1, self.conv2], 0.1)
def forward(self, x):
identity = x
out = F.relu(self.conv1(x), inplace=True)
out = self.conv2(out)
return identity + out
def flow_warp(x, flow, interp_mode='bilinear', padding_mode='zeros'):
"""Warp an image or feature map with optical flow
Args:
x (Tensor): size (N, C, H, W)
flow (Tensor): size (N, H, W, 2), normal value
interp_mode (str): 'nearest' or 'bilinear'
padding_mode (str): 'zeros' or 'border' or 'reflection'
Returns:
Tensor: warped image or feature map
"""
flow = flow.permute(0,2,3,1)
assert x.size()[-2:] == flow.size()[1:3]
B, C, H, W = x.size()
# mesh grid
grid_y, grid_x = torch.meshgrid(torch.arange(0, H), torch.arange(0, W))
grid = torch.stack((grid_x, grid_y), 2).float() # W(x), H(y), 2
grid.requires_grad = False
grid = grid.type_as(x)
vgrid = grid + flow
# scale grid to [-1,1]
vgrid_x = 2.0 * vgrid[:, :, :, 0] / max(W - 1, 1) - 1.0
vgrid_y = 2.0 * vgrid[:, :, :, 1] / max(H - 1, 1) - 1.0
vgrid_scaled = torch.stack((vgrid_x, vgrid_y), dim=3)
output = F.grid_sample(x, vgrid_scaled, mode=interp_mode, padding_mode=padding_mode)
return output |