Polotno to Vector PDF

Convert polotno JSON into vector PDF file from NodeJS with optional PDF/X-1a print-ready export.

npm install @polotno/pdf-export

Basic Usage

import fs from 'fs';
import { jsonToPDF } from '@polotno/pdf-export';

async function run() {
  const json = JSON.parse(fs.readFileSync('./polotno.json'));

  // Standard PDF export
  await jsonToPDF(json, './output.pdf');
}

run();

PDF/X-1a Print-Ready Export

For professional printing, use the PDF/X-1a option which ensures:

• CMYK color space conversion
• Transparency flattening
• Font embedding/outlining
• Print industry compliance

// PDF/X-1a export
await jsonToPDF(json, './print-ready.pdf', {
  pdfx1a: true,
});

// PDF/X-1a with custom metadata
await jsonToPDF(json, './book-cover.pdf', {
  pdfx1a: true,
  validate: true, // Optional validation
  metadata: {
    title: 'My Book Cover',
    author: 'Author Name',
    application: 'KDP CoverCreator v1.0',
  },
});

Spot Color / Foil Support

For professional printing with special inks like metallic foils, Pantone colors, or other spot colors:

await jsonToPDF(json, './output.pdf', {
  pdfx1a: true,
  spotColors: {
    // Map any color to a spot color
    'rgba(255,215,0,1)': {
      name: 'Gold Foil',
      type: 'pantone',
      pantoneCode: 'Pantone 871 C', // Optional reference
      cmyk: [0, 0.15, 0.5, 0], // CMYK fallback (0-1 range)
    },
    '#C0C0C0': {
      name: 'Silver Foil',
      type: 'custom',
      cmyk: [0, 0, 0, 0.25],
    },
  },
});

How it works:

• Any element with a matching fill or stroke color is automatically converted to use the spot color
• Colors are matched flexibly - '#FFD700', '#ffd700', and 'rgba(255,215,0,1)' all match
• Spot colors are preserved as separation color spaces in PDF/X-1a output
• CMYK fallback values are used when viewers don't support spot colors
• Works with all element types: text, shapes, lines, and SVG elements

Color Format Support:

• Hex: '#FFD700' or '#ffd700'
• RGB: 'rgb(255,215,0)'
• RGBA: 'rgba(255,215,0,1)'

Tips:

• Use professional color references (like Pantone codes) to communicate exact requirements to printers
• Provide accurate CMYK fallback values for preview and proof prints
• Spot colors work best with PDF/X-1a export enabled
• You can verify spot colors in Adobe Acrobat by checking Output Preview > Separations

DPI Handling

The library automatically handles DPI conversion to ensure correct physical dimensions in the output PDF. By default, it uses the dpi value from your JSON file (or 72 DPI if not specified).

// JSON with dpi specified
const json = {
  width: 1920,
  height: 1080,
  dpi: 300, // 300 DPI input
  // ... rest of JSON
};

// Use JSON dpi automatically
await jsonToPDF(json, './output.pdf');

// Override DPI via attrs (takes precedence over JSON dpi)
await jsonToPDF(json, './output.pdf', {
  dpi: 150, // Override to 150 DPI
});

How it works:

• Input JSON coordinates are in pixels at the specified DPI
• PDF uses points (1 point = 1/72 inch)
• The library converts: points = pixels × (72 / dpi)
• This ensures the PDF has correct physical dimensions for printing
• All element positions, sizes, and coordinates are automatically scaled

Example:

• A 1920×1080 pixel canvas at 300 DPI = 6.4" × 3.6" in the PDF
• The same canvas at 72 DPI = 26.67" × 15" in the PDF

Requirements

• GhostScript must be installed for PDF/X-1a conversion
• macOS: brew install ghostscript
• Ubuntu: apt-get install ghostscript
• Windows: Download from ghostscript.com

Development

npm run build  # Build the library
npm test       # Run tests