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Merge pull request #568 from christianlouis/copilot/add-multi-language-ocr-support

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feat(ocr): per-pipeline language override for multi-language OCR
This commit is contained in:
Christian Krakau-Louis
2026-03-08 23:11:41 +01:00
committed by GitHub
parent 2e241dd5f3 0b291995b9
commit 6376b6d73b
9 changed files with 816 additions and 19 deletions
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app/utils/ocr_provider.py
+141 -5
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@@ -192,6 +192,95 @@ class OCRResult:
)
# ---------------------------------------------------------------------------
# Multi-language support
# ---------------------------------------------------------------------------
#: Canonical list of supported OCR languages for pipeline configuration.
#: Keys are display names; values are Tesseract language code(s).
#: Tesseract codes are used as the canonical format because they are the most
#: widely applicable across self-hosted providers (Tesseract + ocrmypdf).
#: "auto" falls back to the global ``tesseract_language`` / ``easyocr_languages``
#: settings (i.e. no per-call override).
OCR_LANGUAGES: Dict[str, str] = {
"Auto (use system default)": "auto",
"Arabic": "ara",
"Chinese (Simplified)": "chi_sim",
"Chinese (Traditional)": "chi_tra",
"Czech": "ces",
"Danish": "dan",
"Dutch": "nld",
"English": "eng",
"Finnish": "fin",
"French": "fra",
"German": "deu",
"Greek": "ell",
"Hebrew": "heb",
"Hindi": "hin",
"Hungarian": "hun",
"Italian": "ita",
"Japanese": "jpn",
"Korean": "kor",
"Norwegian": "nor",
"Polish": "pol",
"Portuguese": "por",
"Romanian": "ron",
"Russian": "rus",
"Spanish": "spa",
"Swedish": "swe",
"Thai": "tha",
"Turkish": "tur",
"Ukrainian": "ukr",
"Vietnamese": "vie",
}
#: Mapping from Tesseract language codes to EasyOCR language codes.
#: Used when ``TesseractOCRProvider``-style codes are specified but EasyOCR is
#: the active provider. Codes not present in this map are passed through as-is
#: (EasyOCR accepts its own ISO 639-1 codes such as ``"en"`` or ``"de"``).
TESSERACT_TO_EASYOCR: Dict[str, str] = {
"ara": "ar",
"ces": "cs",
"chi_sim": "ch_sim",
"chi_tra": "ch_tra",
"dan": "da",
"deu": "de",
"ell": "el",
"eng": "en",
"fin": "fi",
"fra": "fr",
"heb": "he",
"hin": "hi",
"hun": "hu",
"ita": "it",
"jpn": "ja",
"kor": "ko",
"nld": "nl",
"nor": "no",
"pol": "pl",
"por": "pt",
"ron": "ro",
"rus": "ru",
"spa": "es",
"swe": "sv",
"tha": "th",
"tur": "tr",
"ukr": "uk",
"vie": "vi",
}
def _tesseract_codes_to_easyocr(tesseract_lang: str) -> List[str]:
"""Convert a Tesseract language string (e.g. ``"eng+deu"``) to a list of
EasyOCR language codes (e.g. ``["en", "de"]``).
Unknown codes are passed through unchanged, so native EasyOCR codes such
as ``"en"`` also work transparently.
"""
codes = [part.strip() for part in tesseract_lang.split("+") if part.strip()]
return [TESSERACT_TO_EASYOCR.get(code, code) for code in codes]
class OCRProvider(ABC):
"""Abstract base class for OCR providers.
@@ -290,10 +379,24 @@ class TesseractOCRProvider(OCRProvider):
- ``tesseract_cmd`` – path to the ``tesseract`` binary (optional).
- ``tesseract_language`` – Tesseract language code(s), e.g. ``"eng"`` or
``"eng+deu"`` (default: ``"eng"``).
The optional *language* constructor argument overrides the global
``tesseract_language`` setting for this specific provider instance, enabling
per-pipeline language configuration.
"""
name = "tesseract"
def __init__(self, language: Optional[str] = None) -> None:
"""Initialise the Tesseract provider.
Args:
language: Optional Tesseract language code(s) to use instead of the
global ``tesseract_language`` setting (e.g. ``"eng+deu"``).
Pass ``None`` or ``"auto"`` to use the global setting.
"""
self._language_override: Optional[str] = language if language and language != "auto" else None
def process(self, file_path: str) -> OCRResult:
try:
import pytesseract
@@ -308,7 +411,7 @@ class TesseractOCRProvider(OCRProvider):
if tesseract_cmd:
pytesseract.pytesseract.tesseract_cmd = tesseract_cmd
lang = getattr(settings, "tesseract_language", None) or "eng"
lang = self._language_override or getattr(settings, "tesseract_language", None) or "eng"
# Ensure language data files are present; attempt download if missing.
from app.utils.ocr_language_manager import ensure_tesseract_languages # noqa: PLC0415
@@ -349,10 +452,26 @@ class EasyOCRProvider(OCRProvider):
- ``easyocr_languages`` – comma-separated list of language codes
(default: ``"en"``).
- ``easyocr_gpu`` – whether to use GPU acceleration (default: ``False``).
The optional *language* constructor argument accepts a Tesseract-style
language string (e.g. ``"eng+deu"``) which is automatically translated to
EasyOCR codes (e.g. ``["en", "de"]``), overriding the global
``easyocr_languages`` setting for this provider instance.
"""
name = "easyocr"
def __init__(self, language: Optional[str] = None) -> None:
"""Initialise the EasyOCR provider.
Args:
language: Optional Tesseract-style language code(s) (e.g. ``"eng+deu"``)
or a comma-separated EasyOCR language list (e.g. ``"en,de"``).
Pass ``None`` or ``"auto"`` to use the global ``easyocr_languages``
setting.
"""
self._language_override: Optional[str] = language if language and language != "auto" else None
def process(self, file_path: str) -> OCRResult:
try:
import easyocr
@@ -363,8 +482,12 @@ class EasyOCRProvider(OCRProvider):
"Install them with: pip install easyocr pdf2image"
) from exc
lang_str = getattr(settings, "easyocr_languages", None) or "en"
langs = [lang.strip() for lang in lang_str.split(",") if lang.strip()]
if self._language_override:
# Convert Tesseract-style codes to EasyOCR codes
langs = _tesseract_codes_to_easyocr(self._language_override)
else:
lang_str = getattr(settings, "easyocr_languages", None) or "en"
langs = [lang.strip() for lang in lang_str.split(",") if lang.strip()]
gpu = getattr(settings, "easyocr_gpu", False)
logger.info(f"[EasyOCR] Processing {os.path.basename(file_path)} (langs={langs}, gpu={gpu})")
@@ -679,23 +802,36 @@ KNOWN_OCR_PROVIDERS: List[str] = sorted(_PROVIDER_MAP.keys())
MAX_OCR_TEXT_FOR_AI_MERGE = 4000
def get_ocr_providers() -> List[OCRProvider]:
def get_ocr_providers(language: Optional[str] = None) -> List[OCRProvider]:
"""Return a list of configured OCR provider instances.
Reads ``settings.ocr_providers`` (comma-separated provider names) and
returns one instantiated provider per entry. Falls back to ``["azure"]``
when the setting is absent.
Args:
language: Optional Tesseract-style language code(s) (e.g. ``"eng+deu"``)
to override the global language settings for providers that support
per-call language configuration (Tesseract and EasyOCR). Pass
``None`` or ``"auto"`` to use the global settings.
"""
raw = getattr(settings, "ocr_providers", None) or "azure"
provider_names = [name.strip().lower() for name in raw.split(",") if name.strip()]
# Normalise "auto" to None so providers fall back to global settings
effective_language = language if language and language != "auto" else None
providers: List[OCRProvider] = []
for name in provider_names:
cls = _PROVIDER_MAP.get(name)
if cls is None:
logger.warning(f"Unknown OCR provider '{name}' in OCR_PROVIDERS – skipping.")
continue
providers.append(cls())
# Pass language override to providers that support per-call language config
if effective_language is not None and name in ("tesseract", "easyocr"):
providers.append(cls(language=effective_language))
else:
providers.append(cls())
logger.debug(f"Registered OCR provider: {name}")
if not providers: