5 files changed, 27 insertions, 6 deletions
diff --git a/src/text_recognizer/datasets/dataset.py b/src/text_recognizer/datasets/dataset.py
index 95063bc..e794605 100644
--- a/src/text_recognizer/datasets/dataset.py
+++ b/src/text_recognizer/datasets/dataset.py
@@ -22,6 +22,7 @@ class Dataset(data.Dataset):
         init_token: Optional[str] = None,
         pad_token: Optional[str] = None,
         eos_token: Optional[str] = None,
+        lower: bool = False,
     ) -> None:
         """Initialization of Dataset class.
 
@@ -33,6 +34,7 @@ class Dataset(data.Dataset):
             init_token (Optional[str]): String representing the start of sequence token. Defaults to None.
             pad_token (Optional[str]): String representing the pad token. Defaults to None.
             eos_token (Optional[str]): String representing the end of sequence token. Defaults to None.
+            lower (bool): Only use lower case letters. Defaults to False.
 
         Raises:
             ValueError: If subsample_fraction is not None and outside the range (0, 1).
@@ -47,7 +49,7 @@ class Dataset(data.Dataset):
         self.subsample_fraction = subsample_fraction
 
         self._mapper = EmnistMapper(
-            init_token=init_token, eos_token=eos_token, pad_token=pad_token
+            init_token=init_token, eos_token=eos_token, pad_token=pad_token, lower=lower
         )
         self._input_shape = self._mapper.input_shape
         self._output_shape = self._mapper._num_classes
diff --git a/src/text_recognizer/datasets/emnist_lines_dataset.py b/src/text_recognizer/datasets/emnist_lines_dataset.py
index eddf341..1992446 100644
--- a/src/text_recognizer/datasets/emnist_lines_dataset.py
+++ b/src/text_recognizer/datasets/emnist_lines_dataset.py
@@ -44,6 +44,7 @@ class EmnistLinesDataset(Dataset):
         init_token: Optional[str] = None,
         pad_token: Optional[str] = None,
         eos_token: Optional[str] = None,
+        lower: bool = False,
     ) -> None:
         """Set attributes and loads the dataset.
 
@@ -60,6 +61,7 @@ class EmnistLinesDataset(Dataset):
             init_token (Optional[str]): String representing the start of sequence token. Defaults to None.
             pad_token (Optional[str]): String representing the pad token. Defaults to None.
             eos_token (Optional[str]): String representing the end of sequence token. Defaults to None.
+            lower (bool): If True, convert uppercase letters to lowercase. Otherwise, use both upper and lowercase.
 
         """
         self.pad_token = "_" if pad_token is None else pad_token
@@ -72,6 +74,7 @@ class EmnistLinesDataset(Dataset):
             init_token=init_token,
             pad_token=self.pad_token,
             eos_token=eos_token,
+            lower=lower,
         )
 
         # Extract dataset information.
diff --git a/src/text_recognizer/datasets/iam_lines_dataset.py b/src/text_recognizer/datasets/iam_lines_dataset.py
index 5ae142c..1cb84bd 100644
--- a/src/text_recognizer/datasets/iam_lines_dataset.py
+++ b/src/text_recognizer/datasets/iam_lines_dataset.py
@@ -35,6 +35,7 @@ class IamLinesDataset(Dataset):
         init_token: Optional[str] = None,
         pad_token: Optional[str] = None,
         eos_token: Optional[str] = None,
+        lower: bool = False,
     ) -> None:
         self.pad_token = "_" if pad_token is None else pad_token
 
@@ -46,6 +47,7 @@ class IamLinesDataset(Dataset):
             init_token=init_token,
             pad_token=pad_token,
             eos_token=eos_token,
+            lower=lower,
         )
 
     @property
diff --git a/src/text_recognizer/datasets/transforms.py b/src/text_recognizer/datasets/transforms.py
index 016ec80..8956b01 100644
--- a/src/text_recognizer/datasets/transforms.py
+++ b/src/text_recognizer/datasets/transforms.py
@@ -93,3 +93,12 @@ class Squeeze:
     def __call__(self, x: Tensor) -> Tensor:
         """Removes first dim."""
         return x.squeeze(0)
+
+
+class ToLower:
+    """Converts target to lower case."""
+
+    def __call__(self, target: Tensor) -> Tensor:
+        """Corrects index value in target tensor."""
+        device = target.device
+        return torch.stack([x - 26 if x > 35 else x for x in target]).to(device)
diff --git a/src/text_recognizer/datasets/util.py b/src/text_recognizer/datasets/util.py
index bf5e772..da87756 100644
--- a/src/text_recognizer/datasets/util.py
+++ b/src/text_recognizer/datasets/util.py
@@ -1,17 +1,14 @@
 """Util functions for datasets."""
 import hashlib
-import importlib
 import json
 import os
 from pathlib import Path
 import string
-from typing import Callable, Dict, List, Optional, Type, Union
-from urllib.request import urlopen, urlretrieve
+from typing import Dict, List, Optional, Union
+from urllib.request import urlretrieve
 
-import cv2
 from loguru import logger
 import numpy as np
-from PIL import Image
 import torch
 from torch import Tensor
 from torchvision.datasets import EMNIST
@@ -50,11 +47,13 @@ class EmnistMapper:
         pad_token: str,
         init_token: Optional[str] = None,
         eos_token: Optional[str] = None,
+        lower: bool = False,
     ) -> None:
         """Loads the emnist essentials file with the mapping and input shape."""
         self.init_token = init_token
         self.pad_token = pad_token
         self.eos_token = eos_token
+        self.lower = lower
 
         self.essentials = self._load_emnist_essentials()
         # Load dataset information.
@@ -120,6 +119,12 @@ class EmnistMapper:
     def _augment_emnist_mapping(self) -> None:
         """Augment the mapping with extra symbols."""
         # Extra symbols in IAM dataset
+        if self.lower:
+            self._mapping = {
+                k: str(v)
+                for k, v in enumerate(list(range(10)) + list(string.ascii_lowercase))
+            }
+
         extra_symbols = [
             " ",
             "!",