24253ac15e
Backend changes: - Apply background image + invisible text layer to all Direct Track PDFs - Add CHART to regions_to_avoid for text extraction - Improve visual fidelity for native PDFs and Office documents Frontend changes: - Remove JSON, UnifiedDocument, Markdown download buttons - Simplify to 2-column layout with only Layout PDF and Reflow PDF - Remove translation JSON download and Layout PDF option - Keep only Reflow PDF for translated document downloads - Clean up unused imports (FileJson, Database, FileOutput) Archives two OpenSpec proposals: - unify-direct-track-pdf-rendering - simplify-frontend-export-options 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
55 lines
2.4 KiB
Markdown
55 lines
2.4 KiB
Markdown
# Change: Unify Direct Track PDF Rendering with Background Image + Invisible Text Layer
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## Why
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Direct Track PDF generation currently has visual rendering issues:
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1. **Chart text overlap**: Text elements extracted from PDF text layer (e.g., "Temperature, °C") overlap with chart images
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2. **Z-order problems**: White text on dark backgrounds becomes invisible when rendered incorrectly
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3. **Office document issues**: PPT/DOC/XLS converted PDFs lose visual fidelity (vector graphics, gradients)
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The root cause is that Direct Track tries to render individual elements (text, images, tables) separately, which leads to z-order conflicts and missing visual content.
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## What Changes
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### Backend Changes
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1. **Unified Background Image Rendering for All Direct Track**
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- Render source PDF page as full-page background image (2x resolution)
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- Draw invisible text layer on top (PDF Text Rendering Mode 3)
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- Text remains searchable/extractable but doesn't visually overlap
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2. **Chart Region Exclusion**
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- Add `CHART` element type to `regions_to_avoid`
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- Chart-internal text (axis labels, legends) will NOT be in invisible text layer
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- These texts are already visible in the background image and don't need translation
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3. **Skip Element Rendering When Background Exists**
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- When background image is rendered, skip individual image/table rendering
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- Only draw invisible text layer for searchability and translation extraction
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### Frontend Considerations
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1. **No UI Changes Required for Layout PDF**
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- Layout PDF generation is automatic, no user options needed
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- Visual output will match source PDF exactly
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2. **Translation Flow Clarification**
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- Layout PDF: Background image + invisible text (for preview)
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- Translated PDF: Reflow layout with real visible text (page-by-page)
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- Chart text excluded from translation (already in background image)
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## Impact
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- **Affected specs**: document-processing, result-export, translation
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- **Affected code**:
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- `backend/app/services/pdf_generator_service.py` (main changes)
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- `backend/app/services/direct_extraction_engine.py` (chart detection)
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- **File size**: Output PDF will be larger due to embedded page images (~2MB per page at 2x resolution)
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- **Processing time**: Slight increase for page rendering
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## Migration
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- No database changes required
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- No API changes required
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- Existing tasks can be re-exported with new PDF generation logic
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