feat: create PDF layout restoration proposal

Create new OpenSpec change proposal to fix critical PDF generation issues: **Problems Identified**: 1. Images never saved (empty _save_image implementation) 2. Image path mismatch (saved_path vs path lookup) 3. Tables never render (fake image dependency) 4. Text style completely lost (no font/color application) **Solution Design**: - Phase 1: Critical fixes (images, tables) - Phase 2: Basic style preservation - Phase 3: Advanced layout features - Phase 4: Testing and optimization **Key Improvements**: - Implement actual image saving in pp_structure_enhanced - Fix path resolution with fallback logic - Use table's own bbox instead of fake images - Track-specific rendering (rich for Direct, simple for OCR) - Preserve StyleInfo (fonts, sizes, colors) **Implementation Tasks**: - 10 major task groups - 4-week timeline - No breaking changes - Performance target: <10% overhead Proposal validated: openspec validate pdf-layout-restoration ✓ 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
2025-11-20 19:00:49 +08:00
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+# Implementation Tasks: PDF Layout Restoration
+
+## Phase 1: Critical Fixes (P0 - Immediate)
+
+### 1. Fix Image Handling
+- [ ] 1.1 Implement `_save_image()` in pp_structure_enhanced.py
+  - [ ] 1.1.1 Create imgs subdirectory in result_dir
+  - [ ] 1.1.2 Handle both file path and numpy array inputs
+  - [ ] 1.1.3 Save with element_id as filename
+  - [ ] 1.1.4 Return relative path for reference
+  - [ ] 1.1.5 Add error handling and logging
+- [ ] 1.2 Fix path resolution in pdf_generator_service.py
+  - [ ] 1.2.1 Create `_get_image_path()` helper with fallback logic
+  - [ ] 1.2.2 Check saved_path, path, image_path keys
+  - [ ] 1.2.3 Check metadata for path
+  - [ ] 1.2.4 Update convert_unified_document_to_ocr_data to use helper
+- [ ] 1.3 Test image rendering
+  - [ ] 1.3.1 Test with OCR track document
+  - [ ] 1.3.2 Test with Direct track document
+  - [ ] 1.3.3 Verify images appear in PDF output
+
+### 2. Fix Table Rendering
+- [ ] 2.1 Remove dependency on fake image references
+  - [ ] 2.1.1 Stop creating fake table_*.png references
+  - [ ] 2.1.2 Remove image lookup in draw_table_region
+- [ ] 2.2 Use direct bbox from table element
+  - [ ] 2.2.1 Get bbox from table_element.get("bbox")
+  - [ ] 2.2.2 Fallback to bbox_polygon if needed
+  - [ ] 2.2.3 Implement _polygon_to_bbox converter
+- [ ] 2.3 Fix table HTML rendering
+  - [ ] 2.3.1 Parse HTML content from table element
+  - [ ] 2.3.2 Position table using normalized bbox
+  - [ ] 2.3.3 Render with proper dimensions
+- [ ] 2.4 Test table rendering
+  - [ ] 2.4.1 Test simple tables
+  - [ ] 2.4.2 Test complex multi-column tables
+  - [ ] 2.4.3 Test with both tracks
+
+## Phase 2: Basic Style Preservation (P1 - Week 1)
+
+### 3. Implement Style Application System
+- [ ] 3.1 Create font mapping system
+  - [ ] 3.1.1 Define FONT_MAPPING dictionary
+  - [ ] 3.1.2 Map common fonts to PDF standard fonts
+  - [ ] 3.1.3 Add fallback to Helvetica for unknown fonts
+- [ ] 3.2 Implement _apply_text_style() method
+  - [ ] 3.2.1 Extract font family from StyleInfo
+  - [ ] 3.2.2 Handle bold/italic flags
+  - [ ] 3.2.3 Apply font size
+  - [ ] 3.2.4 Apply text color
+  - [ ] 3.2.5 Handle errors gracefully
+- [ ] 3.3 Create color parsing utilities
+  - [ ] 3.3.1 Parse hex colors (#RRGGBB)
+  - [ ] 3.3.2 Parse RGB tuples
+  - [ ] 3.3.3 Convert to PDF color space
+
+### 4. Track-Specific Rendering
+- [ ] 4.1 Add track detection in generate_from_unified_document
+  - [ ] 4.1.1 Check unified_doc.metadata.processing_track
+  - [ ] 4.1.2 Route to appropriate rendering method
+- [ ] 4.2 Implement _generate_direct_track_pdf
+  - [ ] 4.2.1 Process each page with style preservation
+  - [ ] 4.2.2 Apply StyleInfo to text elements
+  - [ ] 4.2.3 Use precise positioning
+  - [ ] 4.2.4 Preserve line breaks
+- [ ] 4.3 Implement _generate_ocr_track_pdf
+  - [ ] 4.3.1 Use simplified rendering
+  - [ ] 4.3.2 Best-effort positioning
+  - [ ] 4.3.3 Estimated font sizes
+- [ ] 4.4 Test track-specific rendering
+  - [ ] 4.4.1 Compare Direct track with original
+  - [ ] 4.4.2 Verify OCR track maintains quality
+
+## Phase 3: Advanced Layout (P2 - Week 2)
+
+### 5. Enhanced Text Rendering
+- [ ] 5.1 Implement line-by-line rendering
+  - [ ] 5.1.1 Split text content by newlines
+  - [ ] 5.1.2 Calculate line height from font size
+  - [ ] 5.1.3 Render each line with proper spacing
+- [ ] 5.2 Add paragraph handling
+  - [ ] 5.2.1 Detect paragraph boundaries
+  - [ ] 5.2.2 Apply paragraph spacing
+  - [ ] 5.2.3 Handle indentation
+- [ ] 5.3 Implement text alignment
+  - [ ] 5.3.1 Support left/right/center/justify
+  - [ ] 5.3.2 Calculate positioning based on alignment
+  - [ ] 5.3.3 Apply to each text block
+
+### 6. List Formatting
+- [ ] 6.1 Detect list elements
+  - [ ] 6.1.1 Identify list items from metadata
+  - [ ] 6.1.2 Determine list type (ordered/unordered)
+  - [ ] 6.1.3 Extract indent level
+- [ ] 6.2 Render lists with proper formatting
+  - [ ] 6.2.1 Add bullets/numbers
+  - [ ] 6.2.2 Apply indentation
+  - [ ] 6.2.3 Maintain list spacing
+
+### 7. Span-Level Rendering (Advanced)
+- [ ] 7.1 Extract span information from Direct track
+  - [ ] 7.1.1 Parse children elements for spans
+  - [ ] 7.1.2 Get per-span styling
+  - [ ] 7.1.3 Track position within line
+- [ ] 7.2 Render mixed-style lines
+  - [ ] 7.2.1 Switch styles mid-line
+  - [ ] 7.2.2 Handle inline formatting
+  - [ ] 7.2.3 Preserve exact positioning
+
+## Phase 4: Testing and Optimization (P2 - Week 3)
+
+### 8. Comprehensive Testing
+- [ ] 8.1 Create test suite for layout preservation
+  - [ ] 8.1.1 Unit tests for each component
+  - [ ] 8.1.2 Integration tests for full pipeline
+  - [ ] 8.1.3 Visual regression tests
+- [ ] 8.2 Test with various document types
+  - [ ] 8.2.1 Scientific papers (complex layout)
+  - [ ] 8.2.2 Business documents (tables/charts)
+  - [ ] 8.2.3 Books (chapters/paragraphs)
+  - [ ] 8.2.4 Forms (precise positioning)
+- [ ] 8.3 Performance testing
+  - [ ] 8.3.1 Measure generation time
+  - [ ] 8.3.2 Profile memory usage
+  - [ ] 8.3.3 Identify bottlenecks
+
+### 9. Performance Optimization
+- [ ] 9.1 Implement caching
+  - [ ] 9.1.1 Cache font metrics
+  - [ ] 9.1.2 Cache parsed styles
+  - [ ] 9.1.3 Reuse computed layouts
+- [ ] 9.2 Optimize image handling
+  - [ ] 9.2.1 Lazy load images
+  - [ ] 9.2.2 Compress when appropriate
+  - [ ] 9.2.3 Stream large images
+- [ ] 9.3 Batch operations
+  - [ ] 9.3.1 Group similar rendering ops
+  - [ ] 9.3.2 Minimize context switches
+  - [ ] 9.3.3 Use efficient data structures
+
+### 10. Documentation and Deployment
+- [ ] 10.1 Update API documentation
+  - [ ] 10.1.1 Document new rendering capabilities
+  - [ ] 10.1.2 Add examples of improved output
+  - [ ] 10.1.3 Note performance characteristics
+- [ ] 10.2 Create migration guide
+  - [ ] 10.2.1 Explain improvements
+  - [ ] 10.2.2 Note any breaking changes
+  - [ ] 10.2.3 Provide rollback instructions
+- [ ] 10.3 Deployment preparation
+  - [ ] 10.3.1 Feature flag setup
+  - [ ] 10.3.2 Monitoring metrics
+  - [ ] 10.3.3 Rollback plan
+
+## Success Criteria
+
+### Must Have (Phase 1)
+- [x] Images appear in generated PDFs
+- [x] Tables render with correct layout
+- [x] No regression in existing functionality
+
+### Should Have (Phase 2)
+- [ ] Text styling preserved in Direct track
+- [ ] Font sizes and colors applied
+- [ ] Line breaks maintained
+
+### Nice to Have (Phase 3-4)
+- [ ] Paragraph formatting
+- [ ] List rendering
+- [ ] Span-level styling
+- [ ] <10% performance overhead
+
+## Timeline
+
+- **Week 0**: Phase 1 - Critical fixes (images, tables)
+- **Week 1**: Phase 2 - Basic style preservation
+- **Week 2**: Phase 3 - Advanced layout features
+- **Week 3**: Phase 4 - Testing and optimization
+- **Week 4**: Review, documentation, and deployment