src/models/unet.py

import torch
from torch import nn


class UNet(nn.Module):
    def __init__(self) -> None:
        super().__init__()
        self.mean = [0.485, 0.456, 0.406]
        self.std = [0.229, 0.224, 0.225]
        # Downsampler
        self.enc_conv0 = nn.Sequential(
            nn.Conv2d(in_channels=3, out_channels=64, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(64),
            nn.Conv2d(in_channels=64, out_channels=64, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(64),
            nn.Conv2d(in_channels=64, out_channels=64, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(64)
        )
        self.pool0 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.enc_conv1 = nn.Sequential(
            nn.Conv2d(in_channels=64, out_channels=128, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(128),
            nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(128),
            nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(128)
        )
        self.pool1 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.enc_conv2 = nn.Sequential(
            nn.Conv2d(in_channels=128, out_channels=256, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(256),
            nn.Conv2d(in_channels=256, out_channels=256, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(256),
            nn.Conv2d(in_channels=256, out_channels=256, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(256)
        )
        self.pool2 = nn.MaxPool2d(kernel_size=2, stride=2)
        self.enc_conv3 = nn.Sequential(
            nn.Conv2d(in_channels=256, out_channels=512, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(512),
            nn.Conv2d(in_channels=512, out_channels=512, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(512),
            nn.Conv2d(in_channels=512, out_channels=512, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(512)
        )
        self.pool3 = nn.MaxPool2d(kernel_size=2, stride=2)
        
        # bottleneck
        self.bottleneck_conv = nn.Sequential(
            nn.Conv2d(in_channels=512, out_channels=1024, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(1024),
            nn.Conv2d(in_channels=1024, out_channels=1024, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(1024),
            nn.Conv2d(in_channels=1024, out_channels=1024, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(1024)
        )
        
        # Upsampler

        self.upsample0 = nn.Sequential(
            nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True),
            nn.Conv2d(in_channels=1024, out_channels=512, kernel_size=3, padding=1),
        )
        
        self.dec_conv0 = nn.Sequential(
            nn.Conv2d(in_channels=1024, out_channels=512, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(512),
            nn.Conv2d(in_channels=512, out_channels=512, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(512),
            nn.Conv2d(in_channels=512, out_channels=512, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(512)
        )

        self.upsample1 = nn.Sequential(
            nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True),
            nn.Conv2d(in_channels=512, out_channels=256, kernel_size=3, padding=1),
        )
        
        self.dec_conv1 = nn.Sequential(
            nn.Conv2d(in_channels=512, out_channels=256, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(256),
            nn.Conv2d(in_channels=256, out_channels=256, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(256),
            nn.Conv2d(in_channels=256, out_channels=256, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(256)
        )

        self.upsample2 = nn.Sequential(
            nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True),
            nn.Conv2d(in_channels=256, out_channels=128, kernel_size=3, padding=1),
        )
        
        self.dec_conv2 = nn.Sequential(
            nn.Conv2d(in_channels=256, out_channels=128, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(128),
            nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(128),
            nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(128)
        )

        self.upsample3 = nn.Sequential(
            nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True),
            nn.Conv2d(in_channels=128, out_channels=64, kernel_size=3, padding=1),
        )
        
        self.dec_conv3 = nn.Sequential(
            nn.Conv2d(in_channels=128, out_channels=64, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(64),
            nn.Conv2d(in_channels=64, out_channels=64, kernel_size=3, stride=1, padding=1),
            nn.LeakyReLU(inplace=True),
            nn.BatchNorm2d(64),
            nn.Conv2d(in_channels=64, out_channels=18, kernel_size=1, stride=1, padding=0)
        )
        
    def forward(self, x: torch.Tensor) -> torch.Tensor:
        # encoder
        e0 = self.enc_conv0(x)
        e1 = self.pool0(e0)
        e1 = self.enc_conv1(e1)
        e2 = self.pool1(e1)
        e2 = self.enc_conv2(e2)
        e3 = self.pool2(e2)
        e3 = self.enc_conv3(e3)
        
        # bottleneck
        b = self.pool3(e3)
        b = self.bottleneck_conv(b)
        
        # decoder
        d0 = self.upsample0(b)
        d0 = torch.cat([d0, e3], dim=1)
        d0 = self.dec_conv0(d0)

        d1 = self.upsample1(d0)
        d1 = torch.cat([d1, e2], dim=1)
        d1 = self.dec_conv1(d1)

        d2 = self.upsample2(d1)
        d2 = torch.cat([d2, e1], dim=1)
        d2 = self.dec_conv2(d2)

        d3 = self.upsample3(d2)
        d3 = torch.cat([d3, e0], dim=1)
        d3 = self.dec_conv3(d3)
        return d3