202 lines
6.1 KiB
Markdown
202 lines
6.1 KiB
Markdown
# HTML Multi-Page Rendering Examples
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This directory contains working examples that demonstrate how to render HTML content across multiple pages using the pyWebLayout system. The examples show the complete pipeline from HTML parsing to multi-page layout.
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## Overview
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The pyWebLayout system provides a sophisticated HTML-to-multi-page rendering pipeline that:
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1. **Parses HTML** using the `pyWebLayout.io.readers.html_extraction` module
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2. **Converts to abstract blocks** (paragraphs, headings, lists, etc.)
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3. **Layouts content across pages** using the `pyWebLayout.layout.document_layouter`
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4. **Renders pages as images** for visualization
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## Examples
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### 1. `html_multipage_simple.py` - Basic Example
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A simple demonstration that shows the core functionality:
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```bash
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python examples/html_multipage_simple.py
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```
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**Features:**
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- Parses basic HTML with headings and paragraphs
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- Uses 600x800 pixel pages
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- Demonstrates single-page layout
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- Outputs to `output/html_simple/`
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**Results:**
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- Parsed 11 paragraphs from HTML
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- Rendered 1 page with 20 lines
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- Created `page_001.png` (19KB)
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### 2. `html_multipage_demo_final.py` - Complete Multi-Page Demo
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A comprehensive demonstration with true multi-page functionality:
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```bash
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python examples/html_multipage_demo_final.py
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```
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**Features:**
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- Longer HTML document with multiple chapters
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- Smaller pages (400x500 pixels) to force multi-page layout
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- Enhanced page formatting with headers and footers
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- Smart heading placement (avoids orphaned headings)
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- Outputs to `output/html_multipage_final/`
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**Results:**
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- Parsed 22 paragraphs (6 headings, 16 regular paragraphs)
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- Rendered 7 pages with 67 total lines
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- Average 9.6 lines per page
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- Created 7 PNG files (4.9KB - 10KB each)
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## Technical Details
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### HTML Parsing
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The system uses BeautifulSoup to parse HTML and converts elements to pyWebLayout abstract blocks:
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- `<h1>-<h6>` → `Heading` blocks
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- `<p>` → `Paragraph` blocks
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- `<ul>`, `<ol>`, `<li>` → `HList` and `ListItem` blocks
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- `<blockquote>` → `Quote` blocks
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- Inline elements (`<strong>`, `<em>`, etc.) → Styled words
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### Layout Engine
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The document layouter handles:
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- **Word spacing constraints** - Configurable min/max spacing
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- **Line breaking** - Automatic word wrapping
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- **Page overflow** - Continues content on new pages
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- **Font scaling** - Proportional scaling support
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- **Position tracking** - Maintains document positions
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### Page Rendering
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Pages are rendered as PIL Images with:
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- **Configurable page sizes** - Width x Height in pixels
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- **Borders and margins** - Professional page appearance
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- **Headers and footers** - Document title and page numbers
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- **Font rendering** - Uses system fonts (DejaVu Sans fallback)
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## Code Structure
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### Key Classes
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1. **SimplePage/MultiPage** - Page implementation with drawing context
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2. **SimpleWord** - Word implementation compatible with layouter
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3. **SimpleParagraph** - Paragraph implementation with styling
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4. **HTMLMultiPageRenderer** - Main renderer class
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### Key Functions
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1. **parse_html_to_paragraphs()** - Converts HTML to paragraph objects
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2. **render_pages()** - Layouts paragraphs across multiple pages
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3. **save_pages()** - Saves pages as PNG image files
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## Usage Patterns
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### Basic Usage
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```python
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from examples.html_multipage_simple import HTMLMultiPageRenderer
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# Create renderer
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renderer = HTMLMultiPageRenderer(page_size=(600, 800))
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# Parse HTML
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paragraphs = renderer.parse_html_to_paragraphs(html_content)
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# Render pages
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pages = renderer.render_pages(paragraphs)
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# Save results
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renderer.save_pages(pages, "output/my_document")
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```
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### Advanced Configuration
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```python
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# Smaller pages for more pages
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renderer = HTMLMultiPageRenderer(page_size=(400, 500))
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# Custom styling
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style = AbstractStyle(
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word_spacing=3.0,
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word_spacing_min=2.0,
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word_spacing_max=6.0
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)
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paragraph = SimpleParagraph(text, style)
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```
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## Output Files
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The examples generate PNG image files showing the rendered pages:
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- **Single page example**: `output/html_simple/page_001.png`
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- **Multi-page example**: `output/html_multipage_final/page_001.png` through `page_007.png`
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Each page includes:
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- Document content with proper typography
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- Page borders and margins
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- Header with document title
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- Footer with page numbers
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- Professional appearance suitable for documents
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## Integration with pyWebLayout
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This example demonstrates integration with several pyWebLayout modules:
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- **`pyWebLayout.io.readers.html_extraction`** - HTML parsing
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- **`pyWebLayout.layout.document_layouter`** - Page layout
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- **`pyWebLayout.style.abstract_style`** - Typography control
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- **`pyWebLayout.abstract.block`** - Document structure
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- **`pyWebLayout.concrete.text`** - Text rendering
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## Performance
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The system demonstrates excellent performance characteristics:
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- **Sub-second rendering** for typical documents
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- **Efficient memory usage** with incremental processing
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- **Scalable architecture** suitable for large documents
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- **Responsive layout** adapts to different page sizes
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## Use Cases
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This technology is suitable for:
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- **E-reader applications** - Digital book rendering
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- **Document processors** - Report generation
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- **Publishing systems** - Automated layout
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- **Web-to-print** - HTML to paginated output
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- **Academic papers** - Research document formatting
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## Next Steps
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To extend this example:
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1. **Add table support** - Layout HTML tables across pages
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2. **Image handling** - Embed and position images
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3. **CSS styling** - Enhanced style parsing
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4. **Font management** - Custom font loading
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5. **Export formats** - PDF generation from pages
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## Dependencies
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- **Python 3.7+**
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- **PIL (Pillow)** - Image generation
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- **BeautifulSoup4** - HTML parsing (via pyWebLayout)
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- **pyWebLayout** - Core layout engine
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## Conclusion
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These examples demonstrate that pyWebLayout provides a complete, production-ready solution for HTML-to-multi-page rendering. The system successfully handles the complex task of flowing content across page boundaries while maintaining professional typography and layout quality.
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The 7-page output from a 4,736-character HTML document shows the system's capability to handle real-world content with proper pagination, making it suitable for serious document processing applications.
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