1 files changed, 60 insertions, 0 deletions
diff --git a/text_recognizer/data/mappings/emnist_mapping.py b/text_recognizer/data/mappings/emnist_mapping.py
new file mode 100644
index 0000000..3eed3d8
--- /dev/null
+++ b/text_recognizer/data/mappings/emnist_mapping.py
@@ -0,0 +1,60 @@
+"""Emnist mapping."""
+from typing import List, Optional, Set, Union
+
+import torch
+from torch import Tensor
+
+from text_recognizer.data.mappings.base_mapping import AbstractMapping
+from text_recognizer.data.emnist import emnist_mapping
+
+
+class EmnistMapping(AbstractMapping):
+    """Mapping for EMNIST labels."""
+
+    def __init__(
+        self, extra_symbols: Optional[Set[str]] = None, lower: bool = True
+    ) -> None:
+        self.extra_symbols = set(extra_symbols) if extra_symbols is not None else None
+        self.mapping, self.inverse_mapping, self.input_size = emnist_mapping(
+            self.extra_symbols
+        )
+        if lower:
+            self._to_lower()
+        super().__init__(self.input_size, self.mapping, self.inverse_mapping)
+
+    def _to_lower(self) -> None:
+        """Converts mapping to lowercase letters only."""
+
+        def _filter(x: int) -> int:
+            if 40 <= x:
+                return x - 26
+            return x
+
+        self.inverse_mapping = {v: _filter(k) for k, v in enumerate(self.mapping)}
+        self.mapping = [c for c in self.mapping if not c.isupper()]
+
+    def get_token(self, index: Union[int, Tensor]) -> str:
+        """Returns token for index value."""
+        if (index := int(index)) <= len(self.mapping):
+            return self.mapping[index]
+        raise KeyError(f"Index ({index}) not in mapping.")
+
+    def get_index(self, token: str) -> Tensor:
+        """Returns index value of token."""
+        if token in self.inverse_mapping:
+            return torch.LongTensor([self.inverse_mapping[token]])
+        raise KeyError(f"Token ({token}) not found in inverse mapping.")
+
+    def get_text(self, indices: Union[List[int], Tensor]) -> str:
+        """Returns the text from a list of indices."""
+        if isinstance(indices, Tensor):
+            indices = indices.tolist()
+        return "".join([self.mapping[index] for index in indices])
+
+    def get_indices(self, text: str) -> Tensor:
+        """Returns tensor of indices for a string."""
+        return Tensor([self.inverse_mapping[token] for token in text])
+
+    def __getitem__(self, x: Union[int, Tensor]) -> str:
+        """Returns text for a list of indices."""
+        return self.get_token(x)