import torch
import torch.nn as nn
from torchvision import models
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def convrelu(in_channels, out_channels, kernel, padding):
return nn.Sequential(
nn.Conv2d(in_channels, out_channels, kernel, padding=padding),
nn.ReLU(inplace=True),
)
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class ResNetUNet(nn.Module):
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def __init__(self, n_class):
super().__init__()
self.base_model = models.resnet18(pretrained=True)
self.base_layers = list(self.base_model.children())
self.layer0 = nn.Sequential(*self.base_layers[:3]) # size=(N, 64, x.H/2, x.W/2)
self.layer0_1x1 = convrelu(64, 64, 1, 0)
self.layer1 = nn.Sequential(
*self.base_layers[3:5]
) # size=(N, 64, x.H/4, x.W/4)
self.layer1_1x1 = convrelu(64, 64, 1, 0)
self.layer2 = self.base_layers[5] # size=(N, 128, x.H/8, x.W/8)
self.layer2_1x1 = convrelu(128, 128, 1, 0)
self.layer3 = self.base_layers[6] # size=(N, 256, x.H/16, x.W/16)
self.layer3_1x1 = convrelu(256, 256, 1, 0)
self.layer4 = self.base_layers[7] # size=(N, 512, x.H/32, x.W/32)
self.layer4_1x1 = convrelu(512, 512, 1, 0)
self.upsample = nn.Upsample(scale_factor=2, mode="bilinear", align_corners=True)
self.conv_up3 = convrelu(256 + 512, 512, 3, 1)
self.conv_up2 = convrelu(128 + 512, 256, 3, 1)
self.conv_up1 = convrelu(64 + 256, 256, 3, 1)
self.conv_up0 = convrelu(64 + 256, 128, 3, 1)
self.conv_original_size0 = convrelu(3, 64, 3, 1)
self.conv_original_size1 = convrelu(64, 64, 3, 1)
self.conv_original_size2 = convrelu(64 + 128, 64, 3, 1)
self.num_classes = n_class
self.conv_last = nn.Conv2d(64, n_class, 1)
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def forward(self, input):
x_original = self.conv_original_size0(input)
x_original = self.conv_original_size1(x_original)
layer0 = self.layer0(input)
layer1 = self.layer1(layer0)
layer2 = self.layer2(layer1)
layer3 = self.layer3(layer2)
layer4 = self.layer4(layer3)
layer4 = self.layer4_1x1(layer4)
x = self.upsample(layer4)
layer3 = self.layer3_1x1(layer3)
x = torch.cat([x, layer3], dim=1)
x = self.conv_up3(x)
x = self.upsample(x)
layer2 = self.layer2_1x1(layer2)
x = torch.cat([x, layer2], dim=1)
x = self.conv_up2(x)
x = self.upsample(x)
layer1 = self.layer1_1x1(layer1)
x = torch.cat([x, layer1], dim=1)
x = self.conv_up1(x)
x = self.upsample(x)
layer0 = self.layer0_1x1(layer0)
x = torch.cat([x, layer0], dim=1)
x = self.conv_up0(x)
x = self.upsample(x)
x = torch.cat([x, x_original], dim=1)
x = self.conv_original_size2(x)
out = self.conv_last(x)
return out