feat(ocr): add self-hosted OCR engine support (Tesseract, EasyOCR) with multi-provider cross-checking

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/config.py

@@ -72,6 +72,40 @@ class Settings(BaseSettings):
     azure_region: str
     azure_endpoint: str
     gotenberg_url: str
+
+    # ---------------------------------------------------------------------------
+    # OCR provider settings
+    # ---------------------------------------------------------------------------
+    # Comma-separated list of OCR engines to use.
+    # Supported values: azure, tesseract, easyocr, mistral, google_docai, aws_textract
+    # When multiple engines are listed all are run and results are merged.
+    # Example: OCR_PROVIDERS=azure,tesseract
+    ocr_providers: str = "azure"
+
+    # Strategy for merging results from multiple OCR providers.
+    # - ai_merge  : Ask the AI model to produce the best merged text (default).
+    # - longest   : Return the result with the most characters.
+    # - primary   : Return only the first provider's result (no merging).
+    ocr_merge_strategy: str = "ai_merge"
+
+    # Tesseract OCR settings (used when "tesseract" is in OCR_PROVIDERS)
+    tesseract_cmd: Optional[str] = None  # Path to tesseract binary (e.g. /usr/bin/tesseract)
+    tesseract_language: str = "eng"  # Tesseract language code(s), e.g. "eng" or "eng+deu"
+
+    # EasyOCR settings (used when "easyocr" is in OCR_PROVIDERS)
+    easyocr_languages: str = "en"  # Comma-separated language codes, e.g. "en,de,fr"
+    easyocr_gpu: bool = False  # Enable GPU acceleration for EasyOCR
+
+    # Mistral OCR settings (used when "mistral" is in OCR_PROVIDERS)
+    mistral_api_key: Optional[str] = None
+    mistral_ocr_model: str = "mistral-ocr-latest"
+
+    # Google Cloud Document AI settings (used when "google_docai" is in OCR_PROVIDERS)
+    # Falls back to google_drive_credentials_json for service account credentials.
+    google_docai_credentials_json: Optional[str] = None
+    google_docai_project_id: Optional[str] = None
+    google_docai_processor_id: Optional[str] = None
+    google_docai_location: str = "us"  # Processor location, e.g. "us" or "eu"
     external_hostname: str = "localhost"  # Default to localhost
 
     # Authentication settings

app/tasks/process_document.py

@@ -17,6 +17,7 @@ from app.tasks.extract_metadata_with_gpt import extract_metadata_with_gpt
 from app.tasks.process_with_azure_document_intelligence import (
     process_with_azure_document_intelligence,
 )
+from app.tasks.process_with_ocr import process_with_ocr
 from app.tasks.retry_config import BaseTaskWithRetry
 from app.utils import get_unique_filepath_with_counter, hash_file, log_task_progress
 
@@ -313,7 +314,7 @@ def process_document(
             "Queued for forced OCR processing",
             file_id=file_id,
         )
-        process_with_azure_document_intelligence.delay(new_filename, file_id)
+        process_with_ocr.delay(new_filename, file_id)
         return {"file": new_local_path, "status": "Queued for forced OCR", "file_id": file_id}
 
     # If the file is not a PDF, skip embedded text check and convert to PDF first
@@ -411,12 +412,12 @@ def process_document(
             file_id=file_id,
         )
 
-        # Mark Azure OCR as skipped since we extracted text locally
+        # Mark OCR as skipped since we extracted text locally
         log_task_progress(
             task_id,
             "process_with_azure_document_intelligence",
             "skipped",
-            "Local text extraction succeeded, Azure OCR not needed",
+            "Local text extraction succeeded, OCR not needed",
             file_id=file_id,
         )
 
@@ -436,8 +437,8 @@ def process_document(
             "file_id": file_id,
         }
 
-    # 3. If no embedded text, queue Azure Document Intelligence processing
-    logger.info(f"[{task_id}] No embedded text found. Queueing Azure Document Intelligence processing")
+    # 3. If no embedded text, queue OCR processing
+    logger.info(f"[{task_id}] No embedded text found. Queueing OCR processing")
     log_task_progress(
         task_id,
         "check_text",
@@ -446,12 +447,12 @@ def process_document(
         file_id=file_id,
     )
 
-    # Mark local text extraction as skipped since we're using Azure OCR
+    # Mark local text extraction as skipped since we're using cloud OCR
     log_task_progress(
         task_id,
         "extract_text",
         "skipped",
-        "No embedded text, using Azure OCR instead",
+        "No embedded text, using OCR instead",
         file_id=file_id,
     )
 
@@ -462,5 +463,5 @@ def process_document(
         "Queued for OCR processing",
         file_id=file_id,
     )
-    process_with_azure_document_intelligence.delay(new_filename, file_id)
+    process_with_ocr.delay(new_filename, file_id)
     return {"file": new_local_path, "status": "Queued for OCR", "file_id": file_id}

app/tasks/process_with_ocr.py

@@ -0,0 +1,139 @@
+#!/usr/bin/env python3
+"""Unified OCR processing task for DocuElevate.
+
+This task replaces the single-provider ``process_with_azure_document_intelligence``
+task with a multi-engine OCR pipeline that:
+
+1. Runs every OCR provider listed in ``OCR_PROVIDERS`` (default: ``azure``).
+2. Merges/cross-checks the results using the configured AI model when more
+   than one provider is active (see ``OCR_MERGE_STRATEGY``).
+3. Writes the best searchable PDF back to the working directory.
+4. Hands off to the page-rotation and metadata-extraction pipeline exactly as
+   the legacy Azure task did.
+"""
+
+import logging
+import os
+from typing import Optional
+
+from app.celery_app import celery
+from app.config import settings
+from app.tasks.retry_config import BaseTaskWithRetry
+from app.tasks.rotate_pdf_pages import rotate_pdf_pages
+from app.utils import log_task_progress
+from app.utils.ocr_provider import OCRResult, get_ocr_providers, merge_ocr_results
+
+logger = logging.getLogger(__name__)
+
+
+@celery.task(base=BaseTaskWithRetry, bind=True)
+def process_with_ocr(self, filename: str, file_id: Optional[int] = None):
+    """Run the configured OCR providers on *filename* and continue the pipeline.
+
+    When multiple OCR providers are configured the results are merged using the
+    AI model (or a simpler strategy controlled by ``OCR_MERGE_STRATEGY``).
+
+    Args:
+        filename: Base name of the file inside ``<workdir>/tmp/``.
+        file_id: Optional database record ID passed through to downstream tasks.
+    """
+    task_id = self.request.id
+    log_task_progress(
+        task_id,
+        "process_with_ocr",
+        "in_progress",
+        f"Starting OCR for {filename}",
+        file_id=file_id,
+    )
+
+    try:
+        tmp_file_path = os.path.join(settings.workdir, "tmp", filename)
+        if not os.path.exists(tmp_file_path):
+            raise FileNotFoundError(f"Local file not found: {tmp_file_path}")
+
+        providers = get_ocr_providers()
+        provider_names = [p.name for p in providers]
+        logger.info(f"[{task_id}] Running {len(providers)} OCR provider(s): {provider_names}")
+
+        log_task_progress(
+            task_id,
+            "run_ocr_providers",
+            "in_progress",
+            f"Running OCR providers: {', '.join(provider_names)}",
+            file_id=file_id,
+        )
+
+        results = []
+        errors = []
+        for provider in providers:
+            pname = provider.__class__.__name__
+            try:
+                logger.info(f"[{task_id}] Running {pname} on {filename}")
+                result: OCRResult = provider.process(tmp_file_path)
+                results.append(result)
+                logger.info(f"[{task_id}] {pname} extracted {len(result.text)} chars")
+            except Exception as exc:
+                logger.error(f"[{task_id}] {pname} failed for {filename}: {exc}")
+                errors.append(f"{pname}: {exc}")
+
+        if not results:
+            error_summary = "; ".join(errors)
+            log_task_progress(
+                task_id,
+                "run_ocr_providers",
+                "failure",
+                "All OCR providers failed",
+                file_id=file_id,
+                detail=error_summary,
+            )
+            raise RuntimeError(f"All OCR providers failed for {filename}: {error_summary}")
+
+        if errors:
+            logger.warning(f"[{task_id}] Some OCR providers failed: {'; '.join(errors)}")
+
+        log_task_progress(
+            task_id,
+            "run_ocr_providers",
+            "success",
+            f"{len(results)} of {len(providers)} OCR provider(s) succeeded",
+            file_id=file_id,
+        )
+
+        # Merge results (no-op when only one provider succeeded)
+        extracted_text, searchable_pdf_path, rotation_data = merge_ocr_results(results, filename)
+        logger.info(
+            f"[{task_id}] Merged OCR text: {len(extracted_text)} chars, "
+            f"pdf={'yes' if searchable_pdf_path else 'no'}, "
+            f"rotations={len(rotation_data)}"
+        )
+
+        log_task_progress(
+            task_id,
+            "process_with_ocr",
+            "success",
+            f"OCR complete for {filename}",
+            file_id=file_id,
+            detail=f"Extracted {len(extracted_text)} chars using {len(results)} provider(s)",
+        )
+
+        # Continue pipeline: rotate pages (if needed), then extract metadata
+        rotate_pdf_pages.delay(filename, extracted_text, rotation_data, file_id)
+
+        return {
+            "file": filename,
+            "searchable_pdf": searchable_pdf_path or tmp_file_path,
+            "cleaned_text": extracted_text,
+            "providers_used": [r.provider for r in results],
+        }
+
+    except Exception as exc:
+        logger.error(f"[{task_id}] OCR failed for {filename}: {exc}")
+        log_task_progress(
+            task_id,
+            "process_with_ocr",
+            "failure",
+            f"OCR failed for {filename}",
+            file_id=file_id,
+            detail=str(exc),
+        )
+        raise

app/utils/ocr_provider.py

@@ -0,0 +1,545 @@
+#!/usr/bin/env python3
+"""OCR provider abstraction layer for DocuElevate.
+
+This module provides a pluggable abstraction for various OCR engines, allowing
+the platform to work with Azure Document Intelligence, Tesseract, EasyOCR,
+Mistral OCR, Google Cloud Document AI, and AWS Textract without being locked to
+a single vendor.
+
+Provider selection is controlled by the ``OCR_PROVIDERS`` environment variable
+(comma-separated list, e.g. ``azure,tesseract``).  When multiple providers are
+specified, all enabled providers run in parallel and the results are
+cross-checked by the configured AI model to produce the best final output.
+"""
+
+import logging
+import os
+from abc import ABC, abstractmethod
+from typing import Any, Dict, List, Optional, Tuple
+
+from app.config import settings
+
+logger = logging.getLogger(__name__)
+
+
+class OCRResult:
+    """Container for a single OCR provider's output.
+
+    Attributes:
+        provider: Name of the OCR provider (e.g. ``"azure"``, ``"tesseract"``).
+        text: The extracted plain text.
+        searchable_pdf_path: Optional path to a searchable PDF produced by the
+            provider.  ``None`` when the provider does not produce PDFs.
+        rotation_data: Optional dict mapping page indices to detected rotation
+            angles (same format used by the Azure task).
+        metadata: Provider-specific metadata dict (e.g. confidence scores).
+    """
+
+    def __init__(
+        self,
+        provider: str,
+        text: str,
+        searchable_pdf_path: Optional[str] = None,
+        rotation_data: Optional[Dict[int, float]] = None,
+        metadata: Optional[Dict[str, Any]] = None,
+    ) -> None:
+        self.provider = provider
+        self.text = text
+        self.searchable_pdf_path = searchable_pdf_path
+        self.rotation_data = rotation_data or {}
+        self.metadata = metadata or {}
+
+    def __repr__(self) -> str:
+        return (
+            f"OCRResult(provider={self.provider!r}, "
+            f"chars={len(self.text)}, "
+            f"has_pdf={self.searchable_pdf_path is not None})"
+        )
+
+
+class OCRProvider(ABC):
+    """Abstract base class for OCR providers.
+
+    Concrete providers must implement :meth:`process`, which accepts a path to a
+    PDF file and returns an :class:`OCRResult`.
+
+    Subclasses should also set :attr:`name` to a short, stable identifier
+    (e.g. ``"azure"``, ``"tesseract"``).
+    """
+
+    #: Short, stable identifier for this provider.  Must match the key used in
+    #: :data:`_PROVIDER_MAP` and in the ``OCR_PROVIDERS`` setting.
+    name: str = "unknown"
+
+    @abstractmethod
+    def process(self, file_path: str) -> OCRResult:
+        """Run OCR on *file_path* and return an :class:`OCRResult`.
+
+        Args:
+            file_path: Absolute path to the input PDF file.
+
+        Returns:
+            An :class:`OCRResult` with the extracted text and optional
+            searchable-PDF path.
+
+        Raises:
+            Exception: If OCR processing fails.
+        """
+
+
+# ---------------------------------------------------------------------------
+# Provider implementations
+# ---------------------------------------------------------------------------
+
+
+class AzureOCRProvider(OCRProvider):
+    """OCR via Azure Document Intelligence (the existing provider).
+
+    Credentials are read from ``settings.azure_ai_key`` and
+    ``settings.azure_endpoint``.
+    """
+
+    name = "azure"
+
+    def process(self, file_path: str) -> OCRResult:
+        import azure.core.exceptions
+        from azure.ai.documentintelligence import DocumentIntelligenceClient
+        from azure.ai.documentintelligence.models import AnalyzeOutputOption
+        from azure.core.credentials import AzureKeyCredential
+
+        if not settings.azure_ai_key:
+            raise ValueError("AZURE_AI_KEY must be set when using the Azure OCR provider.")
+        if not settings.azure_endpoint:
+            raise ValueError("AZURE_ENDPOINT must be set when using the Azure OCR provider.")
+
+        client = DocumentIntelligenceClient(
+            endpoint=settings.azure_endpoint,
+            credential=AzureKeyCredential(settings.azure_ai_key),
+        )
+
+        with open(file_path, "rb") as f:
+            poller = client.begin_analyze_document("prebuilt-read", body=f, output=[AnalyzeOutputOption.PDF])
+        result = poller.result()
+        operation_id = poller.details["operation_id"]
+
+        # Extract rotation data
+        rotation_data: Dict[int, float] = {}
+        if hasattr(result, "pages") and result.pages:
+            for i, page in enumerate(result.pages):
+                if hasattr(page, "angle") and page.angle is not None and page.angle != 0:
+                    rotation_data[i] = page.angle
+
+        # Retrieve searchable PDF
+        response = client.get_analyze_result_pdf(model_id=result.model_id, result_id=operation_id)
+        searchable_pdf_path = file_path  # overwrite in place
+        with open(searchable_pdf_path, "wb") as writer:
+            writer.writelines(response)
+
+        extracted_text = result.content if result.content else ""
+        logger.info(f"[AzureOCR] Extracted {len(extracted_text)} chars from {os.path.basename(file_path)}")
+
+        return OCRResult(
+            provider="azure",
+            text=extracted_text,
+            searchable_pdf_path=searchable_pdf_path,
+            rotation_data=rotation_data,
+        )
+
+
+class TesseractOCRProvider(OCRProvider):
+    """OCR via Tesseract (self-hosted, open-source).
+
+    Requires ``pytesseract`` and ``Pillow`` to be installed, plus the
+    Tesseract binary on the system.
+
+    Config knobs (from :class:`~app.config.Settings`):
+    - ``tesseract_cmd`` – path to the ``tesseract`` binary (optional).
+    - ``tesseract_language`` – Tesseract language code(s), e.g. ``"eng"`` or
+      ``"eng+deu"`` (default: ``"eng"``).
+    """
+
+    name = "tesseract"
+
+    def process(self, file_path: str) -> OCRResult:
+        try:
+            import pytesseract
+            from pdf2image import convert_from_path
+        except ImportError as exc:
+            raise RuntimeError(
+                "pytesseract and pdf2image are required for the Tesseract OCR provider. "
+                "Install them with: pip install pytesseract pdf2image"
+            ) from exc
+
+        tesseract_cmd = getattr(settings, "tesseract_cmd", None)
+        if tesseract_cmd:
+            pytesseract.pytesseract.tesseract_cmd = tesseract_cmd
+
+        lang = getattr(settings, "tesseract_language", None) or "eng"
+
+        logger.info(f"[TesseractOCR] Processing {os.path.basename(file_path)} (lang={lang})")
+        pages = convert_from_path(file_path, dpi=300)
+        texts: List[str] = []
+        for i, page_img in enumerate(pages):
+            page_text = pytesseract.image_to_string(page_img, lang=lang)
+            texts.append(page_text)
+            logger.debug(f"[TesseractOCR] Page {i + 1}: {len(page_text)} chars")
+
+        extracted_text = "\n".join(texts)
+        logger.info(f"[TesseractOCR] Extracted {len(extracted_text)} chars total")
+
+        return OCRResult(
+            provider="tesseract",
+            text=extracted_text,
+        )
+
+
+class EasyOCRProvider(OCRProvider):
+    """OCR via EasyOCR (self-hosted, deep-learning based).
+
+    Requires the ``easyocr`` package to be installed.
+
+    Config knobs (from :class:`~app.config.Settings`):
+    - ``easyocr_languages`` – comma-separated list of language codes
+      (default: ``"en"``).
+    - ``easyocr_gpu`` – whether to use GPU acceleration (default: ``False``).
+    """
+
+    name = "easyocr"
+
+    def process(self, file_path: str) -> OCRResult:
+        try:
+            import easyocr
+            from pdf2image import convert_from_path
+        except ImportError as exc:
+            raise RuntimeError(
+                "easyocr and pdf2image are required for the EasyOCR provider. "
+                "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()]
+        gpu = getattr(settings, "easyocr_gpu", False)
+
+        logger.info(f"[EasyOCR] Processing {os.path.basename(file_path)} (langs={langs}, gpu={gpu})")
+        reader = easyocr.Reader(langs, gpu=gpu)
+        pages = convert_from_path(file_path, dpi=300)
+        texts: List[str] = []
+        for i, page_img in enumerate(pages):
+            result = reader.readtext(page_img, detail=0, paragraph=True)
+            page_text = "\n".join(result)
+            texts.append(page_text)
+            logger.debug(f"[EasyOCR] Page {i + 1}: {len(page_text)} chars")
+
+        extracted_text = "\n".join(texts)
+        logger.info(f"[EasyOCR] Extracted {len(extracted_text)} chars total")
+
+        return OCRResult(
+            provider="easyocr",
+            text=extracted_text,
+        )
+
+
+class MistralOCRProvider(OCRProvider):
+    """OCR via Mistral's document understanding API.
+
+    Uses the ``mistral-ocr-latest`` model (or ``settings.mistral_ocr_model``)
+    via the OpenAI-compatible messages API.
+
+    Config knobs (from :class:`~app.config.Settings`):
+    - ``mistral_api_key`` – Mistral API key.
+    - ``mistral_ocr_model`` – model name (default: ``"mistral-ocr-latest"``).
+    """
+
+    name = "mistral"
+
+    def process(self, file_path: str) -> OCRResult:
+        import base64
+
+        try:
+            import openai
+        except ImportError as exc:
+            raise RuntimeError("openai package is required for the Mistral OCR provider.") from exc
+
+        api_key = getattr(settings, "mistral_api_key", None)
+        if not api_key:
+            raise ValueError("MISTRAL_API_KEY must be set when using the Mistral OCR provider.")
+
+        model = getattr(settings, "mistral_ocr_model", None) or "mistral-ocr-latest"
+        base_url = "https://api.mistral.ai/v1"
+
+        logger.info(f"[MistralOCR] Processing {os.path.basename(file_path)} with {model}")
+
+        with open(file_path, "rb") as f:
+            pdf_b64 = base64.b64encode(f.read()).decode("utf-8")
+
+        client = openai.OpenAI(api_key=api_key, base_url=base_url)
+        response = client.chat.completions.create(
+            model=model,
+            messages=[
+                {
+                    "role": "user",
+                    "content": [
+                        {
+                            "type": "image_url",
+                            "image_url": {"url": f"data:application/pdf;base64,{pdf_b64}"},
+                        },
+                        {
+                            "type": "text",
+                            "text": "Extract all text from this document. Return only the extracted text, preserving structure.",
+                        },
+                    ],
+                }
+            ],
+        )
+        extracted_text = response.choices[0].message.content or ""
+        logger.info(f"[MistralOCR] Extracted {len(extracted_text)} chars")
+
+        return OCRResult(provider="mistral", text=extracted_text)
+
+
+class GoogleDocAIOCRProvider(OCRProvider):
+    """OCR via Google Cloud Document AI.
+
+    Config knobs (from :class:`~app.config.Settings`):
+    - ``google_docai_credentials_json`` – Service account JSON (optional;
+      falls back to ``google_drive_credentials_json`` or ADC).
+    - ``google_docai_project_id`` – GCP project ID (required).
+    - ``google_docai_processor_id`` – Document AI processor ID (required).
+    - ``google_docai_location`` – processor location, e.g. ``"us"`` (default:
+      ``"us"``).
+    """
+
+    name = "google_docai"
+
+    def process(self, file_path: str) -> OCRResult:
+        try:
+            from google.cloud import documentai
+            from google.oauth2 import service_account
+        except ImportError as exc:
+            raise RuntimeError(
+                "google-cloud-documentai is required for the Google Document AI OCR provider. "
+                "Install it with: pip install google-cloud-documentai"
+            ) from exc
+
+        import json
+
+        project_id = getattr(settings, "google_docai_project_id", None)
+        processor_id = getattr(settings, "google_docai_processor_id", None)
+        location = getattr(settings, "google_docai_location", None) or "us"
+
+        if not project_id or not processor_id:
+            raise ValueError(
+                "GOOGLE_DOCAI_PROJECT_ID and GOOGLE_DOCAI_PROCESSOR_ID must be set "
+                "when using the Google Document AI OCR provider."
+            )
+
+        # Credentials: prefer dedicated docai key, then fall back to gdrive SA key
+        creds_json = getattr(settings, "google_docai_credentials_json", None) or getattr(
+            settings, "google_drive_credentials_json", None
+        )
+
+        creds = None
+        if creds_json:
+            try:
+                creds_info = json.loads(creds_json)
+                creds = service_account.Credentials.from_service_account_info(
+                    creds_info,
+                    scopes=["https://www.googleapis.com/auth/cloud-platform"],
+                )
+            except Exception as e:
+                logger.warning(f"[GoogleDocAIOCR] Failed to parse credentials JSON: {e}; using ADC")
+
+        client_options = {"api_endpoint": f"{location}-documentai.googleapis.com"}
+        client = documentai.DocumentProcessorServiceClient(
+            credentials=creds,
+            client_options=client_options,
+        )
+
+        processor_name = client.processor_path(project_id, location, processor_id)
+
+        with open(file_path, "rb") as f:
+            raw_document = documentai.RawDocument(content=f.read(), mime_type="application/pdf")
+
+        request = documentai.ProcessRequest(name=processor_name, raw_document=raw_document)
+        result = client.process_document(request=request)
+        document = result.document
+        extracted_text = document.text or ""
+        logger.info(f"[GoogleDocAIOCR] Extracted {len(extracted_text)} chars")
+
+        return OCRResult(provider="google_docai", text=extracted_text)
+
+
+class AWSTextractOCRProvider(OCRProvider):
+    """OCR via AWS Textract.
+
+    Reuses existing AWS credentials from settings (``aws_access_key_id``,
+    ``aws_secret_access_key``, ``aws_region``).
+    """
+
+    name = "aws_textract"
+
+    def process(self, file_path: str) -> OCRResult:
+        try:
+            import boto3
+        except ImportError as exc:
+            raise RuntimeError("boto3 is required for the AWS Textract OCR provider.") from exc
+
+        aws_access_key_id = getattr(settings, "aws_access_key_id", None)
+        aws_secret_access_key = getattr(settings, "aws_secret_access_key", None)
+        region = getattr(settings, "aws_region", None) or "us-east-1"
+
+        if not aws_access_key_id or not aws_secret_access_key:
+            raise ValueError(
+                "AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY must be set " "when using the AWS Textract OCR provider."
+            )
+
+        logger.info(f"[AWSTextract] Processing {os.path.basename(file_path)} (region={region})")
+
+        client = boto3.client(
+            "textract",
+            aws_access_key_id=aws_access_key_id,
+            aws_secret_access_key=aws_secret_access_key,
+            region_name=region,
+        )
+
+        with open(file_path, "rb") as f:
+            document_bytes = f.read()
+
+        response = client.detect_document_text(Document={"Bytes": document_bytes})
+
+        lines: List[str] = []
+        for block in response.get("Blocks", []):
+            if block.get("BlockType") == "LINE":
+                text = block.get("Text", "")
+                if text:
+                    lines.append(text)
+
+        extracted_text = "\n".join(lines)
+        logger.info(f"[AWSTextract] Extracted {len(extracted_text)} chars")
+
+        return OCRResult(provider="aws_textract", text=extracted_text)
+
+
+# ---------------------------------------------------------------------------
+# Factory & multi-provider orchestration
+# ---------------------------------------------------------------------------
+
+_PROVIDER_MAP: Dict[str, type] = {
+    "azure": AzureOCRProvider,
+    "tesseract": TesseractOCRProvider,
+    "easyocr": EasyOCRProvider,
+    "mistral": MistralOCRProvider,
+    "google_docai": GoogleDocAIOCRProvider,
+    "aws_textract": AWSTextractOCRProvider,
+}
+
+# Sorted list of known provider names (kept in sync with _PROVIDER_MAP)
+KNOWN_OCR_PROVIDERS: List[str] = sorted(_PROVIDER_MAP.keys())
+
+# Maximum characters per OCR result sent to the AI for merging.
+# Keeping this bounded prevents excessively large prompts that would exhaust
+# the model's context window or incur high token costs.
+MAX_OCR_TEXT_FOR_AI_MERGE = 4000
+
+
+def get_ocr_providers() -> 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.
+    """
+    raw = getattr(settings, "ocr_providers", None) or "azure"
+    provider_names = [name.strip().lower() for name in raw.split(",") if name.strip()]
+
+    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())
+        logger.debug(f"Registered OCR provider: {name}")
+
+    if not providers:
+        logger.warning("No valid OCR providers configured, falling back to Azure.")
+        providers.append(AzureOCRProvider())
+
+    return providers
+
+
+def merge_ocr_results(results: List[OCRResult], filename: str) -> Tuple[str, Optional[str], Dict[int, float]]:
+    """Select the best text from multiple OCR results.
+
+    When only one result is available the text is returned as-is.  When
+    multiple results exist the AI model is consulted to pick or merge the best
+    version (controlled by ``settings.ocr_merge_strategy``).
+
+    Args:
+        results: Non-empty list of :class:`OCRResult` objects.
+        filename: Document filename used for logging.
+
+    Returns:
+        A 3-tuple of ``(best_text, searchable_pdf_path, rotation_data)`` where
+        *searchable_pdf_path* and *rotation_data* come from the first result
+        that provides them.
+    """
+    if not results:
+        return "", None, {}
+
+    if len(results) == 1:
+        r = results[0]
+        return r.text, r.searchable_pdf_path, r.rotation_data
+
+    strategy = getattr(settings, "ocr_merge_strategy", None) or "ai_merge"
+    logger.info(f"Merging {len(results)} OCR results for {filename} (strategy={strategy})")
+
+    # Best searchable PDF comes from the first provider that produced one
+    searchable_pdf_path = next((r.searchable_pdf_path for r in results if r.searchable_pdf_path), None)
+    # Best rotation data comes from the first provider that detected any
+    rotation_data = next((r.rotation_data for r in results if r.rotation_data), {})
+
+    if strategy == "primary":
+        # Simply return the first result's text
+        return results[0].text, searchable_pdf_path, rotation_data
+
+    if strategy == "longest":
+        best = max(results, key=lambda r: len(r.text))
+        return best.text, searchable_pdf_path, rotation_data
+
+    # Default: ai_merge – ask AI to pick/merge the best text
+    try:
+        from app.utils.ai_provider import get_ai_provider
+
+        provider = get_ai_provider()
+        model = settings.ai_model or settings.openai_model
+
+        extracts_block = "\n\n".join(
+            f"--- OCR Engine: {r.provider} ---\n{r.text[:MAX_OCR_TEXT_FOR_AI_MERGE]}" for r in results
+        )
+        messages = [
+            {
+                "role": "system",
+                "content": (
+                    "You are an expert document editor. You will receive OCR extracts of the same document "
+                    "produced by different OCR engines. Your task is to produce a single, clean, accurate "
+                    "version of the text by cross-referencing all inputs. "
+                    "Fix obvious OCR errors, preserve document structure, and return ONLY the final text."
+                ),
+            },
+            {
+                "role": "user",
+                "content": (
+                    f"Document: {filename}\n\n"
+                    f"The following are OCR extracts from different engines:\n\n{extracts_block}\n\n"
+                    "Please merge these into the most accurate version of the document text."
+                ),
+            },
+        ]
+        merged_text = provider.chat_completion(messages, model=model, temperature=0)
+        logger.info(f"AI-merged OCR text: {len(merged_text)} chars for {filename}")
+        return merged_text, searchable_pdf_path, rotation_data
+    except Exception as exc:
+        logger.error(f"AI merge failed for {filename}: {exc}; falling back to longest result")
+        best = max(results, key=lambda r: len(r.text))
+        return best.text, searchable_pdf_path, rotation_data

app/utils/settings_service.py

@@ -14,6 +14,7 @@ from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.orm import Session
 
 from app.models import ApplicationSettings, SettingsAuditLog
+from app.utils.ocr_provider import KNOWN_OCR_PROVIDERS
 
 logger = logging.getLogger(__name__)
 
@@ -280,6 +281,122 @@ SETTING_METADATA = {
         "required": False,
         "restart_required": False,
     },
+    # OCR Engine Configuration
+    "ocr_providers": {
+        "category": "OCR Engines",
+        "description": (
+            "Active OCR engines. Select one or more engines to enable. "
+            "When multiple engines are selected all run in parallel and results are merged. "
+            "Stored as a comma-separated list (e.g. azure,tesseract)."
+        ),
+        "type": "multiselect",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+        "options": KNOWN_OCR_PROVIDERS,
+    },
+    "ocr_merge_strategy": {
+        "category": "OCR Engines",
+        "description": (
+            "Strategy for merging results from multiple OCR providers. "
+            "ai_merge: use AI to produce best merged text (default); "
+            "longest: return the result with most characters; "
+            "primary: return only the first provider's result."
+        ),
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+        "options": ["ai_merge", "longest", "primary"],
+    },
+    # OCR – Tesseract
+    "tesseract_cmd": {
+        "category": "OCR Engines",
+        "description": "Path to the Tesseract binary (e.g. /usr/bin/tesseract). Leave blank to use system PATH.",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "tesseract_language": {
+        "category": "OCR Engines",
+        "description": "Tesseract language code(s), e.g. 'eng' or 'eng+deu'. Default: eng.",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    # OCR – EasyOCR
+    "easyocr_languages": {
+        "category": "OCR Engines",
+        "description": "Comma-separated EasyOCR language codes, e.g. 'en,de,fr'. Default: en.",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "easyocr_gpu": {
+        "category": "OCR Engines",
+        "description": "Enable GPU acceleration for EasyOCR (requires CUDA). Default: False.",
+        "type": "boolean",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    # OCR – Mistral
+    "mistral_api_key": {
+        "category": "OCR Engines",
+        "description": "Mistral API key (required when 'mistral' is in OCR_PROVIDERS).",
+        "type": "string",
+        "sensitive": True,
+        "required": False,
+        "restart_required": False,
+    },
+    "mistral_ocr_model": {
+        "category": "OCR Engines",
+        "description": "Mistral OCR model name. Default: mistral-ocr-latest.",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    # OCR – Google Cloud Document AI
+    "google_docai_credentials_json": {
+        "category": "OCR Engines",
+        "description": (
+            "Google Cloud service account credentials JSON for Document AI "
+            "(optional; falls back to google_drive_credentials_json or Application Default Credentials)."
+        ),
+        "type": "string",
+        "sensitive": True,
+        "required": False,
+        "restart_required": False,
+    },
+    "google_docai_project_id": {
+        "category": "OCR Engines",
+        "description": "GCP project ID for Google Cloud Document AI (required when 'google_docai' is in OCR_PROVIDERS).",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "google_docai_processor_id": {
+        "category": "OCR Engines",
+        "description": "Document AI processor ID (required when 'google_docai' is in OCR_PROVIDERS).",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "google_docai_location": {
+        "category": "OCR Engines",
+        "description": "Document AI processor location (e.g. 'us' or 'eu'). Default: us.",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+        "options": ["us", "eu"],
+    },
     # Storage Providers - Dropbox
     "dropbox_app_key": {
         "category": "Storage Providers",

frontend/templates/settings.html

@@ -139,6 +139,27 @@
                   Enable {{ setting.key.replace('_', ' ').title() }}
                 </label>
               </div>
+              {% elif setting.metadata.type == 'multiselect' and setting.metadata.options %}
+              <!-- Multi-select checkboxes: stored as comma-separated string -->
+              <div class="flex flex-wrap gap-2 mt-1">
+                {% for opt in setting.metadata.options %}
+                <label class="inline-flex items-center gap-1.5 px-3 py-1.5 rounded-full border cursor-pointer select-none
+                              transition-colors
+                              bg-white border-gray-300 hover:border-blue-400"
+                       :class="isSelected('{{ setting.key }}', '{{ opt }}')
+                               ? 'bg-blue-100 border-blue-500 text-blue-800 font-medium'
+                               : 'text-gray-700'">
+                  <input type="checkbox"
+                         class="sr-only"
+                         :checked="isSelected('{{ setting.key }}', '{{ opt }}')"
+                         @change="toggleMultiselect('{{ setting.key }}', '{{ opt }}', $event.target.checked)"
+                  />
+                  <i :class="isSelected('{{ setting.key }}', '{{ opt }}') ? 'fas fa-check-circle text-blue-600' : 'far fa-circle text-gray-400'"></i>
+                  <span class="text-sm">{{ opt }}</span>
+                </label>
+                {% endfor %}
+              </div>
+              <p class="mt-1 text-xs text-gray-400">Effective value: <code x-text="formData['{{ setting.key }}'] || '(none)'"></code></p>
               {% elif setting.metadata.options %}
               <!-- Dropdown Select for fields with a fixed list of values -->
               <select
@@ -280,6 +301,28 @@ function settingsApp() {
       {% endfor %}
     },
 
+    /** Parse a comma-separated multiselect value into a trimmed array. */
+    parseMultiselect(key) {
+      return (this.formData[key] || '').split(',').map(s => s.trim()).filter(Boolean);
+    },
+
+    /** Return true when *option* is present in the comma-separated *key* value. */
+    isSelected(key, option) {
+      return this.parseMultiselect(key).includes(option);
+    },
+
+    /** Add or remove *option* from the comma-separated *key* value. */
+    toggleMultiselect(key, option, checked) {
+      const current = this.parseMultiselect(key);
+      if (checked) {
+        if (!current.includes(option)) current.push(option);
+      } else {
+        const idx = current.indexOf(option);
+        if (idx !== -1) current.splice(idx, 1);
+      }
+      this.formData[key] = current.join(',');
+    },
+
     togglePassword(key) {
       this.showPassword[key] = !this.showPassword[key];
     },

requirements.txt

@@ -37,4 +37,8 @@ paramiko>=3.4.0  # SSH/SFTP implementation for Python (LGPL license)
 apprise>=1.4.0
 
 # AI provider aggregator - enables Anthropic, Gemini, Ollama, and 100+ LLM providers
-litellm>=1.0.0,<2.0.0
+litellm>=1.0.0,<2.0.0
+
+# Self-hosted OCR engines (optional – only required when the provider is enabled)
+pytesseract>=0.3.10  # Python wrapper for Tesseract OCR
+pdf2image>=1.17.0  # Convert PDF pages to images (used by Tesseract and EasyOCR providers)