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import torch
import torch.nn as nn
import torch.nn.functional as F
class DoubleConv(nn.Module):
"""(convolution => [BN] => ReLU) * 2"""
def __init__(self, in_channels, out_channels, mid_channels=None):
super().__init__()
if not mid_channels:
mid_channels = out_channels
self.double_conv = nn.Sequential(
nn.Conv2d(in_channels, mid_channels, kernel_size=3, padding=1, bias=False),
nn.InstanceNorm2d(mid_channels),
nn.ReLU(inplace=True),
nn.Conv2d(mid_channels, out_channels, kernel_size=3, padding=1, bias=False),
nn.InstanceNorm2d(out_channels),
nn.ReLU(inplace=True)
)
def forward(self, x):
return self.double_conv(x)
class Down(nn.Module):
"""Downscaling with maxpool then double conv"""
def __init__(self, in_channels, out_channels):
super().__init__()
self.maxpool_conv = nn.Sequential(
nn.MaxPool2d(2),
DoubleConv(in_channels, out_channels)
)
def forward(self, x):
return self.maxpool_conv(x)
class Up(nn.Module):
"""Upscaling then double conv"""
def __init__(self, in_channels, out_channels):
super().__init__()
self.up = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
self.conv = DoubleConv(in_channels, out_channels, in_channels // 2)
def forward(self, x1, x2=None):
x1 = self.up(x1)
if x2 is not None:
diffY = x2.size()[2] - x1.size()[2]
diffX = x2.size()[3] - x1.size()[3]
x1 = F.pad(x1, [diffX // 2, diffX - diffX // 2,
diffY // 2, diffY - diffY // 2])
x = torch.cat([x2, x1], dim=1)
else:
x = x1
return self.conv(x)
class OutConv(nn.Module):
def __init__(self, in_channels, out_channels):
super(OutConv, self).__init__()
self.conv = nn.Conv2d(in_channels, out_channels, kernel_size=1)
self.act_fn = nn.Sigmoid()
def forward(self, x):
y = self.act_fn(self.conv(x))
return y
class Upsampler(nn.Module):
def __init__(self, input_dim=32, output_dim=3, network_capacity=128):
super(Upsampler, self).__init__()
self.inc = DoubleConv(input_dim, network_capacity * 4)
self.up1 = Up(network_capacity * 4, network_capacity * 2)
self.up2 = Up(network_capacity * 2, network_capacity)
self.outc = OutConv(network_capacity, output_dim)
def forward(self, x):
x = self.inc(x)
x = self.up1(x)
x = self.up2(x)
x = self.outc(x)
return x