modeling_autoencoder.py

import torch
import torch.nn as nn
from .configuration_autoencoder import AutoencoderConfig
from transformers import PreTrainedModel


class Encoder(nn.Module):
    def __init__(self, latent_dim=256):
        super().__init__()

        self.conv = nn.Sequential(
            nn.Conv2d(3, 32, 4, 2, 1),   # 256 → 128
            nn.ReLU(),
            nn.Conv2d(32, 64, 4, 2, 1),  # 128 → 64
            nn.ReLU(),
            nn.Conv2d(64, 128, 4, 2, 1), # 64 → 32
            nn.ReLU(),
        )

        self.flatten = nn.Flatten()
        self.fc = nn.Linear(128 * 32 * 32, latent_dim)

    def forward(self, x):
        x = self.conv(x)
        x = self.flatten(x)
        return self.fc(x)


class Decoder(nn.Module):
    def __init__(self, latent_dim=256):
        super().__init__()

        self.fc = nn.Linear(latent_dim, 128 * 32 * 32)

        self.deconv = nn.Sequential(
            nn.ConvTranspose2d(128, 64, 4, 2, 1),
            nn.ReLU(),
            nn.ConvTranspose2d(64, 32, 4, 2, 1),
            nn.ReLU(),
            nn.ConvTranspose2d(32, 3, 4, 2, 1),
            nn.Sigmoid()
        )

    def forward(self, z):
        x = self.fc(z)
        x = x.view(-1, 128, 32, 32)
        return self.deconv(x)


class Autoencoder(PreTrainedModel):
    config_class = AutoencoderConfig 

    def __init__(self, config):
        super().__init__(config)

        self.encoder = Encoder(config.latent_dim)
        self.decoder = Decoder(config.latent_dim)

        self.post_init()

    def forward(self, x):
        z = self.encoder(x)
        return self.decoder(z)