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feat(ocr): add AI-based embedded text quality check with automatic OCR fallback

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Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
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copilot-swe-agent[bot]
2026-02-24 18:41:27 +00:00
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docs/ConfigurationGuide.md
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@@ -461,6 +461,28 @@ DocuElevate supports multiple OCR engines that can be used individually or in co
When multiple providers are listed, all run in parallel and their results are merged according to `OCR_MERGE_STRATEGY`.
#### Embedded Text Quality Check
DocuElevate can automatically assess whether the text already embedded in a PDF is of sufficient quality before deciding to skip OCR. This prevents poor OCR output from a previous scan being silently used for downstream processing.
| **Variable** | **Description** | **Default** |
|--------------------------------|---------------------------------------------------------------------------------|-------------|
| `ENABLE_TEXT_QUALITY_CHECK` | Enable AI-based quality assessment of embedded PDF text. | `true` |
**How it works:**
1. When a PDF with embedded text is received, DocuElevate first examines the PDF metadata (`/Producer`, `/Creator`).
2. If the PDF was **digitally created** (e.g., exported from Word, LibreOffice, LaTeX, or any modern authoring tool), the embedded text is considered trustworthy and the quality check is skipped — digital text cannot be improved by re-OCRing.
3. If the PDF was **previously OCR'd** (Tesseract, ABBYY, ocrmypdf, etc.) or the origin is **unknown**, an AI model evaluates a sample of the extracted text for:
- Excessive typos and character-substitution artefacts typical of OCR
- Garbage characters or symbol soup
- Incoherent or nonsensical sentences
- Heavy fragmentation
4. If the quality score falls **below 65/100**, the embedded text is discarded and the file is sent to the configured OCR providers for a fresh scan.
5. All quality decisions (score, source, AI feedback) are recorded in the processing log for review.
> **Tip**: Set `ENABLE_TEXT_QUALITY_CHECK=false` to disable the check entirely and always use embedded text as-is. This is useful when the AI provider is unavailable or when processing speed is more important than text accuracy.
#### Searchable PDF Text Layer
Not all OCR providers embed a searchable text layer in the output PDF. The table below summarises each provider's behaviour and how DocuElevate handles it: