dataset.py

import torch
import numpy as np
import pandas as pd
from PIL import Image
from torch.utils.data import Dataset

from augments import RandAug

# Torch dataset
class TextlineDataset(Dataset):
    def __init__(self, root_dir, df, processor, augment=False, max_target_length=128):
        self.root_dir = root_dir
        self.df = df
        self.processor = processor
        self.augment = augment
        self.augmentator = RandAug()
        self.max_target_length = max_target_length

    def __len__(self):
        return len(self.df)

    def __getitem__(self, idx):
        # get file name + text 
        file_name = self.df['file_name'][idx]
        text = self.df['text'][idx]

        # prepare image (i.e. resize + normalize)
        image = Image.open(self.root_dir + file_name).convert("RGB")

        # Add image augmentations
        if self.augment:
            image = self.augmentator(image)

        # extract the pixel values
        pixel_values = self.processor(image, return_tensors="pt").pixel_values
        
        # add labels (input_ids) by encoding the text
        labels = self.processor.tokenizer(str(text), 
                                          padding="max_length", truncation=True, 
                                          max_length=self.max_target_length).input_ids
        # important: make sure that PAD tokens are ignored by the loss function
        labels = [label if label != self.processor.tokenizer.pad_token_id else -100 for label in labels]
        encoding = {"pixel_values": pixel_values.squeeze(), "labels": torch.tensor(labels)}
        return encoding