feat: ocr when too many chars unrecognized

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.2.2-dev0
+
+* Add logic to use OCR when layout text is full of unknown characters
+
 ## 0.2.1
 
 * Refactor to facilitate local inference

test_unstructured_inference/inference/test_layout.py

@@ -176,3 +176,39 @@ def test_process_file_with_model(monkeypatch, mock_page_layout, model_name):
 def test_process_file_with_model_raises_on_invalid_model_name():
     with pytest.raises(models.UnknownModelException):
         layout.process_file_with_model("", model_name="fake")
+
+
+class MockPageLayout(layout.PageLayout):
+    def __init__(self, ocr_text):
+        self.ocr_text = ocr_text
+
+    def ocr(self, text_block):
+        return self.ocr_text
+
+
+class MockTextBlock(lp.TextBlock):
+    def __init__(self, text):
+        self.text = text
+
+
+def test_interpret_text_block_use_ocr_when_text_symbols_cid():
+    fake_text = "(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)"
+    fake_ocr = "ocrme"
+    fake_text_block = MockTextBlock(fake_text)
+    assert MockPageLayout(fake_ocr).interpret_text_block(fake_text_block) == fake_ocr
+
+
+@pytest.mark.parametrize(
+    "text, expected",
+    [("base", 0.0), ("", 0.0), ("(cid:2)", 1.0), ("(cid:1)a", 0.5), ("c(cid:1)ab", 0.25)],
+)
+def test_cid_ratio(text, expected):
+    assert layout.cid_ratio(text) == expected
+
+
+@pytest.mark.parametrize(
+    "text, expected",
+    [("base", False), ("(cid:2)", True), ("(cid:1234567890)", True), ("jkl;(cid:12)asdf", True)],
+)
+def test_is_cid_present(text, expected):
+    assert layout.is_cid_present(text) == expected

unstructured_inference/__version__.py

@@ -1 +1 @@
-__version__ = "0.2.1"  # pragma: no cover
+__version__ = "0.2.2-dev0"  # pragma: no cover

unstructured_inference/inference/layout.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 from dataclasses import dataclass
+import re
 import tempfile
 from typing import List, Optional, Tuple, Union, BinaryIO
 
@@ -109,10 +110,7 @@ def get_elements(self, inplace=True) -> Optional[List[LayoutElement]]:
             text_blocks = self.layout.filter_by(item, center=True)
             text = str()
             for text_block in text_blocks:
-                # NOTE(robinson) - If the text attribute is None, that means the PDF isn't
-                # already OCR'd and we have to send the snippet out for OCRing.
-                if text_block.text is None:
-                    text_block.text = self.ocr(text_block)
+                text_block.text = self.interpret_text_block(text_block)
             text = " ".join([x for x in text_blocks.get_texts() if x])
 
             elements.append(
@@ -124,6 +122,16 @@ def get_elements(self, inplace=True) -> Optional[List[LayoutElement]]:
             return None
         return elements
 
+    def interpret_text_block(self, text_block: lp.TextBlock) -> str:
+        """Interprets the text in a TextBlock."""
+        # NOTE(robinson) - If the text attribute is None, that means the PDF isn't
+        # already OCR'd and we have to send the snippet out for OCRing.
+        if (text_block.text is None) or cid_ratio(text_block.text) > 0.5:
+            out_text = self.ocr(text_block)
+        else:
+            out_text = text_block.text
+        return out_text
+
     def ocr(self, text_block: lp.TextBlock) -> str:
         """Runs a cropped text block image through and OCR agent."""
         logger.debug("Running OCR on text block ...")
@@ -156,3 +164,19 @@ def process_file_with_model(filename: str, model_name: str) -> DocumentLayout:
     model = None if model_name is None else get_model(model_name)
     layout = DocumentLayout.from_file(filename, model=model)
     return layout
+
+
+def cid_ratio(text: str) -> float:
+    """Gets ratio of unknown 'cid' characters extracted from text to all characters."""
+    if not is_cid_present(text):
+        return 0.0
+    cid_pattern = r"\(cid\:(\d+)\)"
+    unmatched, n_cid = re.subn(cid_pattern, "", text)
+    total = n_cid + len(unmatched)
+    return n_cid / total
+
+
+def is_cid_present(text: str) -> bool:
+    if len(text) < len("(cid:x)"):
+        return False
+    return text.find("(cid:") != -1