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feat: Introduce automatic language detection in TesseractOcrCliModel (#800)

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* feat: Introduce automatic language detection in tesseract_ocr_cli model. Extend unit tests.

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* docs: Add example how to use "auto" language with tesseract OCR engines

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* fix: Refactor the TesseractOcrModel and TesseractOcrCliModel to validate if the auto-detected
language is installed in the system and if not fall back to a default option without language.

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

---------

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>
This commit is contained in:
Nikos Livathinos
2025-01-26 08:07:56 +01:00
committed by GitHub
parent 9e4ca90db1
commit 3be2fb581f
6 changed files with 154 additions and 38 deletions
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68
docling/models/tesseract_ocr_model.py
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@@ -8,6 +8,7 @@ from docling.datamodel.document import ConversionResult
from docling.datamodel.pipeline_options import TesseractOcrOptions
from docling.datamodel.settings import settings
from docling.models.base_ocr_model import BaseOcrModel
from docling.utils.ocr_utils import map_tesseract_script
from docling.utils.profiling import TimeRecorder
_log = logging.getLogger(__name__)
@@ -20,6 +21,7 @@ class TesseractOcrModel(BaseOcrModel):
self.scale = 3 # multiplier for 72 dpi == 216 dpi.
self.reader = None
self.osd_reader = None
if self.enabled:
install_errmsg = (
@@ -47,8 +49,8 @@ class TesseractOcrModel(BaseOcrModel):
except:
raise ImportError(install_errmsg)
_, tesserocr_languages = tesserocr.get_languages()
if not tesserocr_languages:
_, self._tesserocr_languages = tesserocr.get_languages()
if not self._tesserocr_languages:
raise ImportError(missing_langs_errmsg)
# Initialize the tesseractAPI
@@ -57,7 +59,7 @@ class TesseractOcrModel(BaseOcrModel):
self.script_readers: dict[str, tesserocr.PyTessBaseAPI] = {}
if any([l.startswith("script/") for l in tesserocr_languages]):
if any([l.startswith("script/") for l in self._tesserocr_languages]):
self.script_prefix = "script/"
else:
self.script_prefix = ""
@@ -72,14 +74,14 @@ class TesseractOcrModel(BaseOcrModel):
tesserocr_kwargs["path"] = self.options.path
if lang == "auto":
self.reader = tesserocr.PyTessBaseAPI(
self.reader = tesserocr.PyTessBaseAPI(**tesserocr_kwargs)
self.osd_reader = tesserocr.PyTessBaseAPI(
**{"lang": "osd", "psm": tesserocr.PSM.OSD_ONLY} | tesserocr_kwargs
)
else:
self.reader = tesserocr.PyTessBaseAPI(
**{"lang": lang} | tesserocr_kwargs,
)
self.reader_RIL = tesserocr.RIL
def __del__(self):
@@ -96,8 +98,6 @@ class TesseractOcrModel(BaseOcrModel):
yield from page_batch
return
import tesserocr
for page in page_batch:
assert page._backend is not None
if not page._backend.is_valid():
@@ -105,6 +105,7 @@ class TesseractOcrModel(BaseOcrModel):
else:
with TimeRecorder(conv_res, "ocr"):
assert self.reader is not None
assert self._tesserocr_languages is not None
ocr_rects = self.get_ocr_rects(page)
@@ -117,43 +118,42 @@ class TesseractOcrModel(BaseOcrModel):
scale=self.scale, cropbox=ocr_rect
)
# Retrieve text snippets with their bounding boxes
self.reader.SetImage(high_res_image)
local_reader = self.reader
if "auto" in self.options.lang:
assert self.osd_reader is not None
if self.options.lang == ["auto"]:
osd = self.reader.DetectOrientationScript()
self.osd_reader.SetImage(high_res_image)
osd = self.osd_reader.DetectOrientationScript()
# No text, probably
if osd is None:
continue
script = osd["script_name"]
script = map_tesseract_script(script)
lang = f"{self.script_prefix}{script}"
if script == "Katakana" or script == "Hiragana":
script = "Japanese"
elif script == "Han":
script = "HanS"
elif script == "Korean":
script = "Hangul"
# Check if the detected languge is present in the system
if lang not in self._tesserocr_languages:
msg = f"Tesseract detected the script '{script}' and language '{lang}'."
msg += " However this language is not installed in your system and will be ignored."
_log.warning(msg)
else:
if script not in self.script_readers:
import tesserocr
_log.debug(
f'Using model for the detected script "{script}"'
)
if script not in self.script_readers:
self.script_readers[script] = tesserocr.PyTessBaseAPI(
path=self.reader.GetDatapath(),
lang=f"{self.script_prefix}{script}",
psm=tesserocr.PSM.AUTO,
init=True,
oem=tesserocr.OEM.DEFAULT,
)
local_reader = self.script_readers[script]
local_reader.SetImage(high_res_image)
else:
local_reader = self.reader
self.script_readers[script] = (
tesserocr.PyTessBaseAPI(
path=self.reader.GetDatapath(),
lang=lang,
psm=tesserocr.PSM.AUTO,
init=True,
oem=tesserocr.OEM.DEFAULT,
)
)
local_reader = self.script_readers[script]
local_reader.SetImage(high_res_image)
boxes = local_reader.GetComponentImages(
self.reader_RIL.TEXTLINE, True
)