snapdom

# SnapDOM Skill

Fast, dependency-free DOM-to-image capture library for converting HTML elements into scalable SVG or raster image formats.

## When to Use This Skill

Use SnapDOM when you need to:
- Convert HTML elements to images (SVG, PNG, JPG, WebP)
- Capture styled DOM with pseudo-elements and shadows
- Export elements with embedded fonts and icons
- Create screenshots with custom dimensions or scaling
- Handle CORS-blocked resources using proxy fallback
- Implement custom rendering pipelines with plugins
- Optimize performance on large or complex elements

## Key Features

### Universal Export Options
- **SVG** - Scalable vector format, embeds all styles
- **PNG, JPG, WebP** - Raster formats with configurable quality
- **Canvas** - Get raw Canvas element for further processing
- **Blob** - Raw binary data for custom handling

### Performance
- Ultra-fast capture (1.6ms for small elements, ~171ms for 4000×2000)
- **No dependencies** - Uses standard Web APIs only
- Outperforms html2canvas by 10-40x on complex elements

### Style Support
- Embedded fonts (including icon fonts)
- CSS pseudo-elements (::before, ::after)
- CSS counters
- CSS line-clamp
- Transform and shadow effects
- Shadow DOM content

### Advanced Capabilities
- Same-origin iframe support
- CORS proxy fallback for blocked assets
- Plugin system for custom transformations
- Straighten transforms (remove rotate/translate)
- Selective element exclusion
- Tight bounding box calculation

## Installation

### NPM/Yarn
```bash
npm install @zumer/snapdom
# or
yarn add @zumer/snapdom
```

### CDN (ES Module)
```html
<script type="module">
  import { snapdom } from "https://unpkg.com/@zumer/snapdom/dist/snapdom.mjs";
</script>
```

### CDN (UMD)
```html
<script src="https://unpkg.com/@zumer/snapdom/dist/snapdom.umd.js"></script>
```

## Quick Start Examples

### Basic Reusable Capture
```javascript
// Create reusable capture object
const result = await snapdom(document.querySelector('#target'));

// Export to different formats
const png = await result.toPng();
const jpg = await result.toJpg();
const svg = await result.toSvg();
const canvas = await result.toCanvas();
const blob = await result.toBlob();

// Use the result
document.body.appendChild(png);
```

### One-Step Export
```javascript
// Direct export without intermediate object
const png = await snapdom.toPng(document.querySelector('#target'));
const svg = await snapdom.toSvg(element);
```

### Download Element
```javascript
// Automatically download as file
await snapdom.download(element, 'screenshot.png');
await snapdom.download(element, 'image.svg');
```

### With Options
```javascript
const result = await snapdom(element, {
  scale: 2,                    // 2x resolution
  width: 800,                  // Custom width
  height: 600,                 // Custom height
  embedFonts: true,            // Include @font-face
  exclude: '.no-capture',      // Hide elements
  useProxy: true,              // Enable CORS proxy
  straighten: true,            // Remove transforms
  noShadows: false             // Keep shadows
});

const png = await result.toPng({ quality: 0.95 });
```

## Essential Options Reference

| Option | Type | Purpose |
|--------|------|---------|
| `scale` | Number | Scale output (e.g., 2 for 2x resolution) |
| `width` | Number | Custom output width in pixels |
| `height` | Number | Custom output height in pixels |
| `embedFonts` | Boolean | Include non-icon @font-face rules |
| `useProxy` | String\|Boolean | Enable CORS proxy (URL or true for default) |
| `exclude` | String | CSS selector for elements to hide |
| `straighten` | Boolean | Remove translate/rotate transforms |
| `noShadows` | Boolean | Strip shadow effects |

## Common Patterns

### Responsive Screenshots
```javascript
// Capture at different scales
const mobile = await snapdom.toPng(element, { scale: 1 });
const tablet = await snapdom.toPng(element, { scale: 1.5 });
const desktop = await snapdom.toPng(element, { scale: 2 });
```

### Exclude Elements
```javascript
// Hide specific elements from capture
const png = await snapdom.toPng(element, {
  exclude: '.controls, .watermark, [data-no-capture]'
});
```

### Fixed Dimensions
```javascript
// Capture with specific size
const result = await snapdom(element, {
  width: 1200,
  height: 630  // Standard social media size
});
```

### CORS Handling
```javascript
// Fallback for CORS-blocked resources
const png = await snapdom.toPng(element, {
  useProxy: 'https://cors.example.com/?' // Custom proxy
});
```

### Plugin System (Beta)
```javascript
// Extend with custom exporters
snapdom.plugins([pluginFactory, { colorOverlay: true }]);

// Hook into lifecycle
defineExports(context) {
  return {
    pdf: async (ctx, opts) => { /* generate PDF */ }
  };
}

// Lifecycle hooks available:
// beforeSnap → beforeClone → afterClone →
// beforeRender → beforeExport → afterExport
```

## Performance Comparison

SnapDOM significantly outperforms html2canvas:

| Scenario | SnapDOM | html2canvas | Improvement |
|----------|---------|-------------|-------------|
| Small (200×100) | 1.6ms | 68ms | 42x faster |
| Medium (800×600) | 12ms | 280ms | 23x faster |
| Large (4000×2000) | 171ms | 1,800ms | 10x faster |

## Development

### Setup
```bash
git clone https://github.com/zumerlab/snapdom.git
cd snapdom
npm install
```

### Build
```bash
npm run compile
```

### Testing
```bash
npm test
```

## Browser Support

- Chrome/Edge 90+
- Firefox 88+
- Safari 14+
- Mobile browsers (iOS Safari 14+, Chrome Mobile)

## Resources

### Documentation
- **Official Website:** https://snapdom.dev/
- **GitHub Repository:** https://github.com/zumerlab/snapdom
- **NPM Package:** https://www.npmjs.com/package/@zumer/snapdom
- **License:** MIT

### scripts/
Add helper scripts here for automation, e.g.:
- `batch-screenshot.js` - Capture multiple elements
- `pdf-export.js` - Convert snapshots to PDF
- `compare-outputs.js` - Compare SVG vs PNG quality

### assets/
Add templates and examples:
- HTML templates for common capture scenarios
- CSS frameworks pre-configured with snapdom
- Boilerplate projects integrating snapdom

## Related Tools

- **html2canvas** - Alternative DOM capture (slower but more compatible)
- **Orbit CSS Toolkit** - Companion toolkit by Zumerlab (https://github.com/zumerlab/orbit)

## Tips & Best Practices

1. **Performance**: Use `scale` instead of `width`/`height` for better performance
2. **Fonts**: Set `embedFonts: true` to ensure custom fonts appear correctly
3. **CORS Issues**: Use `useProxy: true` if images fail to load
4. **Large Elements**: Break into smaller chunks for complex pages
5. **Quality**: For PNG/JPG, use `quality: 0.95` for best quality
6. **SVG Vectors**: Prefer SVG export for charts and graphics

## Troubleshooting

### Elements Not Rendering
- Check if element has sufficient height/width
- Verify CSS is fully loaded before capture
- Try `straighten: false` if transforms are causing issues

### Missing Fonts
- Set `embedFonts: true`
- Ensure fonts are loaded before calling snapdom
- Check browser console for font loading errors

### CORS Issues
- Enable `useProxy: true`
- Use custom proxy URL if default fails
- Check if resources are from same origin

### Performance Issues
- Reduce `scale` value
- Use `noShadows: true` to skip shadow rendering
- Consider splitting large captures into smaller sections