OCR/openspec/changes/archive/2025-12-04-improve-translated-text-fitting/proposal.md

Change: Reflow Layout PDF Export for All Tracks

Why

When generating translated PDFs, text often doesn't fit within original bounding boxes due to language expansion/contraction differences. Additionally, users may want a readable flowing document format even without translation.

Example from task c79df0ad-f9a6-4c04-8139-13eaef25fa83:

• Original Chinese: "华天科技（宝鸡）有限公司设备版块报价单" (19 characters)
• Translated English: "Huatian Technology (Baoji) Co., Ltd. Equipment Division Quotation" (65+ characters)
• Same bounding box: 703×111 pixels
• Current result: Font reduced to minimum (3pt), text unreadable

What Changes

• NEW: Add reflow layout PDF generation for both OCR and Direct tracks
• Preserve semantic structure (headings, tables, lists) in reflow mode
• Use consistent, readable font sizes (12pt body, 16pt headings)
• Embed images inline within flowing content
• IMPORTANT: Original layout preservation PDF generation remains unchanged
• Support both tracks with proper reading order:
  • OCR track: Use existing reading_order array from PP-StructureV3
  • Direct track: Use PyMuPDF's implicit order (with option for column detection)
• FIX: Remove outdated MADLAD-400 references from frontend (now uses Dify cloud translation)

Download Options

Scenario	Layout PDF	Reflow PDF
Without Translation	Available	Available (NEW)
With Translation	-	Available (single option, unchanged)

Impact

• Affected specs: specs/result-export/spec.md
• Affected code:
  • backend/app/services/pdf_generator_service.py - add reflow generation method
  • backend/app/routers/tasks.py - add reflow PDF download endpoint
  • backend/app/routers/translate.py - use reflow mode for translated PDFs
  • frontend/src/pages/TaskDetailPage.tsx:
    • Add "Download Reflow PDF" button for original documents
    • Remove MADLAD-400 badge and outdated description text