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

npm install @zumer/snapdom
# or
yarn add @zumer/snapdom

CDN (ES Module)

<script type="module">
  import { snapdom } from "https://unpkg.com/@zumer/snapdom/dist/snapdom.mjs";
</script>

CDN (UMD)

<script src="https://unpkg.com/@zumer/snapdom/dist/snapdom.umd.js"></script>

Quick Start Examples

Basic Reusable Capture

// 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

// Direct export without intermediate object
const png = await snapdom.toPng(document.querySelector("#target"));
const svg = await snapdom.toSvg(element);

Download Element

// Automatically download as file
await snapdom.download(element, "screenshot.png");
await snapdom.download(element, "image.svg");

With Options

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

Common Patterns

Responsive Screenshots

// 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

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

Fixed Dimensions

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

CORS Handling

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

Plugin System (Beta)

// 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:

Development

Setup

git clone https://github.com/zumerlab/snapdom.git
cd snapdom
npm install

Build

npm run compile

Testing

npm test