lesson-2

Pytorch-Seg/lesson-2/model/unet_model.py

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+""" Full assembly of the parts to form the complete network """
+"""Refer https://github.com/milesial/Pytorch-UNet/blob/master/unet/unet_model.py"""
+
+import torch.nn.functional as F
+
+from unet_parts import *
+
+
+class UNet(nn.Module):
+    def __init__(self, n_channels, n_classes, bilinear=False):
+        super(UNet, self).__init__()
+        self.n_channels = n_channels
+        self.n_classes = n_classes
+        self.bilinear = bilinear
+
+        self.inc = DoubleConv(n_channels, 64)
+        self.down1 = Down(64, 128)
+        self.down2 = Down(128, 256)
+        self.down3 = Down(256, 512)
+        self.down4 = Down(512, 1024)
+        self.up1 = Up(1024, 512, bilinear)
+        self.up2 = Up(512, 256, bilinear)
+        self.up3 = Up(256, 128, bilinear)
+        self.up4 = Up(128, 64, bilinear)
+        self.outc = OutConv(64, n_classes)
+
+    def forward(self, x):
+        x1 = self.inc(x)
+        x2 = self.down1(x1)
+        x3 = self.down2(x2)
+        x4 = self.down3(x3)
+        x5 = self.down4(x4)
+        x = self.up1(x5, x4)
+        x = self.up2(x, x3)
+        x = self.up3(x, x2)
+        x = self.up4(x, x1)
+        logits = self.outc(x)
+        return logits
+
+if __name__ == '__main__':
+    net = UNet(n_channels=3, n_classes=1)
+    print(net)

Pytorch-Seg/lesson-2/model/unet_parts.py

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+""" Parts of the U-Net model """
+"""https://github.com/milesial/Pytorch-UNet/blob/master/unet/unet_parts.py"""
+
+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):
+        super().__init__()
+        self.double_conv = nn.Sequential(
+            nn.Conv2d(in_channels, out_channels, kernel_size=3, padding=0),
+            nn.BatchNorm2d(out_channels),
+            nn.ReLU(inplace=True),
+            nn.Conv2d(out_channels, out_channels, kernel_size=3, padding=0),
+            nn.BatchNorm2d(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, bilinear=True):
+        super().__init__()
+
+        # if bilinear, use the normal convolutions to reduce the number of channels
+        if bilinear:
+            self.up = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
+        else:
+            self.up = nn.ConvTranspose2d(in_channels, in_channels // 2, kernel_size=2, stride=2)
+
+        self.conv = DoubleConv(in_channels, out_channels)
+
+    def forward(self, x1, x2):
+        x1 = self.up(x1)
+        # input is CHW
+        diffY = torch.tensor([x2.size()[2] - x1.size()[2]])
+        diffX = torch.tensor([x2.size()[3] - x1.size()[3]])
+
+        x1 = F.pad(x1, [diffX // 2, diffX - diffX // 2,
+                        diffY // 2, diffY - diffY // 2])
+        # if you have padding issues, see
+        # https://github.com/HaiyongJiang/U-Net-Pytorch-Unstructured-Buggy/commit/0e854509c2cea854e247a9c615f175f76fbb2e3a
+        # https://github.com/xiaopeng-liao/Pytorch-UNet/commit/8ebac70e633bac59fc22bb5195e513d5832fb3bd
+        x = torch.cat([x2, x1], dim=1)
+        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)
+
+    def forward(self, x):
+        return self.conv(x)