OCR/openspec/changes/pdf-layout-restoration/tasks.md

# Implementation Tasks: PDF Layout Restoration

## Phase 1: Critical Fixes (P0 - Immediate)

### 1. Fix Image Handling
- [x] 1.1 Implement `_save_image()` in pp_structure_enhanced.py
  - [x] 1.1.1 Create imgs subdirectory in result_dir
  - [x] 1.1.2 Handle both file path and numpy array inputs
  - [x] 1.1.3 Save with element_id as filename
  - [x] 1.1.4 Return relative path for reference
  - [x] 1.1.5 Add error handling and logging
- [x] 1.2 Fix path resolution in pdf_generator_service.py
  - [x] 1.2.1 Create `_get_image_path()` helper with fallback logic
  - [x] 1.2.2 Check saved_path, path, image_path keys
  - [x] 1.2.3 Check metadata for path
  - [x] 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
- [x] 2.1 Remove dependency on fake image references
  - [x] 2.1.1 Stop creating fake table_*.png references (kept for backward compatibility)
  - [x] 2.1.2 Remove image lookup in draw_table_region (now uses direct bbox first)
- [x] 2.2 Use direct bbox from table element
  - [x] 2.2.1 Get bbox from table_element.get("bbox")
  - [x] 2.2.2 Fallback to bbox_polygon if needed
  - [x] 2.2.3 Implement _polygon_to_bbox converter (inline conversion implemented)
- [x] 2.3 Fix table HTML rendering
  - [x] 2.3.1 Parse HTML content from table element
  - [x] 2.3.2 Position table using normalized bbox
  - [x] 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