1 files changed, 133 insertions, 0 deletions
diff --git a/src/text_recognizer/networks/vqvae/decoder.py b/src/text_recognizer/networks/vqvae/decoder.py
new file mode 100644
index 0000000..8847aba
--- /dev/null
+++ b/src/text_recognizer/networks/vqvae/decoder.py
@@ -0,0 +1,133 @@
+"""CNN decoder for the VQ-VAE."""
+
+from typing import List, Optional, Tuple, Type
+
+import torch
+from torch import nn
+from torch import Tensor
+
+from text_recognizer.networks.util import activation_function
+from text_recognizer.networks.vqvae.encoder import _ResidualBlock
+
+
+class Decoder(nn.Module):
+    """A CNN encoder network."""
+
+    def __init__(
+        self,
+        channels: List[int],
+        kernel_sizes: List[int],
+        strides: List[int],
+        num_residual_layers: int,
+        embedding_dim: int,
+        upsampling: Optional[List[List[int]]] = None,
+        activation: str = "leaky_relu",
+        dropout_rate: float = 0.0,
+    ) -> None:
+        super().__init__()
+
+        if dropout_rate:
+            if activation == "selu":
+                dropout = nn.AlphaDropout(p=dropout_rate)
+            else:
+                dropout = nn.Dropout(p=dropout_rate)
+        else:
+            dropout = None
+
+        self.upsampling = upsampling
+
+        self.res_block = nn.ModuleList([])
+        self.upsampling_block = nn.ModuleList([])
+
+        self.embedding_dim = embedding_dim
+        activation = activation_function(activation)
+
+        # Configure encoder.
+        self.decoder = self._build_decoder(
+            channels, kernel_sizes, strides, num_residual_layers, activation, dropout,
+        )
+
+    def _build_decompression_block(
+        self,
+        in_channels: int,
+        channels: int,
+        kernel_sizes: List[int],
+        strides: List[int],
+        activation: Type[nn.Module],
+        dropout: Optional[Type[nn.Module]],
+    ) -> nn.ModuleList:
+        modules = nn.ModuleList([])
+        configuration = zip(channels, kernel_sizes, strides)
+        for i, (out_channels, kernel_size, stride) in enumerate(configuration):
+            modules.append(
+                nn.Sequential(
+                    nn.ConvTranspose2d(
+                        in_channels,
+                        out_channels,
+                        kernel_size,
+                        stride=stride,
+                        padding=1,
+                    ),
+                    activation,
+                )
+            )
+
+            if i < len(self.upsampling):
+                modules.append(nn.Upsample(size=self.upsampling[i]),)
+
+            if dropout is not None:
+                modules.append(dropout)
+
+            in_channels = out_channels
+
+        modules.extend(
+            nn.Sequential(
+                nn.ConvTranspose2d(
+                    in_channels, 1, kernel_size=kernel_size, stride=stride, padding=1
+                ),
+                nn.Tanh(),
+            )
+        )
+
+        return modules
+
+    def _build_decoder(
+        self,
+        channels: int,
+        kernel_sizes: List[int],
+        strides: List[int],
+        num_residual_layers: int,
+        activation: Type[nn.Module],
+        dropout: Optional[Type[nn.Module]],
+    ) -> nn.Sequential:
+
+        self.res_block.append(
+            nn.Conv2d(self.embedding_dim, channels[0], kernel_size=1, stride=1,)
+        )
+
+        # Bottleneck module.
+        self.res_block.extend(
+            nn.ModuleList(
+                [
+                    _ResidualBlock(channels[0], channels[0], dropout)
+                    for i in range(num_residual_layers)
+                ]
+            )
+        )
+
+        # Decompression module
+        self.upsampling_block.extend(
+            self._build_decompression_block(
+                channels[0], channels[1:], kernel_sizes, strides, activation, dropout
+            )
+        )
+
+        self.res_block = nn.Sequential(*self.res_block)
+        self.upsampling_block = nn.Sequential(*self.upsampling_block)
+
+        return nn.Sequential(self.res_block, self.upsampling_block)
+
+    def forward(self, z_q: Tensor) -> Tensor:
+        """Reconstruct input from given codes."""
+        x_reconstruction = self.decoder(z_q)
+        return x_reconstruction