ts-potrace

ts-potrace

A TypeScript implementation of Potrace — a tool for transforming bitmap images into scalable vector graphics.

Features

• Bitmap Tracing: Convert raster images to clean SVG vector paths
• Posterization: Create multi-level color traces for more detailed output
• High-Quality Output: Generate smooth, optimized vector graphics
• Extensive Customization: Fine-tune the tracing process with many options
• TypeScript Support: Fully typed API for better development experience
• Platform Independent: Works in Bun & Node.js environments

Examples

Original image	Potrace output	Posterized output

(Example image inherited from online demo of the browser version)

Installation

# Using npm
npm install ts-potrace

# Using Bun
bun install ts-potrace

# Using pnpm
pnpm add ts-potrace

# Using Yarn
yarn add ts-potrace

Quick Start

Basic Tracing

import fs from 'node:fs'
import { trace } from 'ts-potrace'

// Simple tracing with default options
trace('input.png', (err, svg) => {
  if (err)
    throw err
  fs.writeFileSync('output.svg', svg)
})

// With custom options
trace('input.png', {
  background: '#f8f9fa',
  color: 'blue',
  threshold: 120
}, (err, svg) => {
  if (err)
    throw err
  fs.writeFileSync('output-custom.svg', svg)
})

Posterization

import fs from 'node:fs'
import { posterize } from 'ts-potrace'

// Create multi-level color trace
posterize('input.png', {
  steps: 5,
  fillStrategy: 'dominant'
}, (err, svg) => {
  if (err)
    throw err
  fs.writeFileSync('posterized.svg', svg)
})

// With custom threshold levels
posterize('input.png', {
  steps: [40, 85, 135, 180]
}, (err, svg) => {
  if (err)
    throw err
  fs.writeFileSync('custom-levels.svg', svg)
})

Advanced Usage

Using the Potrace Class Directly

import fs from 'node:fs'
import { Potrace } from 'ts-potrace'

const potrace = new Potrace({
  turdSize: 5,
  alphaMax: 1,
  optCurve: true,
  optTolerance: 0.2
})

potrace.loadImage('input.png', (err) => {
  if (err)
    throw err

  // Get full SVG document
  const svg = potrace.getSVG()
  fs.writeFileSync('output.svg', svg)

  // Get just the path element
  const path = potrace.getPathTag()
  console.log(path)

  // Get as SVG symbol with ID
  const symbol = potrace.getSymbol('traced-image')
  console.log(symbol)
})

Using the Posterizer Class

import fs from 'node:fs'
import { Posterizer } from 'ts-potrace'

const posterizer = new Posterizer({
  steps: 4,
  fillStrategy: 'dominant',
  rangeDistribution: 'auto',
  background: '#ffffff'
})

posterizer.loadImage('input.png', (err) => {
  if (err)
    throw err

  posterizer.setParameters({
    color: '#333',
    background: '#f0f0f0',
  })

  // Get the SVG with multiple color levels
  const svg = posterizer.getSVG()
  fs.writeFileSync('posterized.svg', svg)

  // Get as SVG symbol with ID
  const symbol = posterizer.getSymbol('posterized-image')
  console.log(symbol)
})

Configuration Parameters

Potrace Parameters

• turnPolicy - How to resolve ambiguities in path decomposition
  • Options: 'black', 'white', 'left', 'right', 'minority', 'majority'
  • Default: 'minority'
• turdSize - Suppress speckles up to this size
  • Default: 2
• alphaMax - Corner threshold parameter
  • Default: 1
• optCurve - Enable curve optimization
  • Default: true
• optTolerance - Curve optimization tolerance
  • Default: 0.2
• threshold - Threshold for black/white classification
  • Range: 0-255 or Potrace.THRESHOLD_AUTO for automatic threshold detection
  • Default: Potrace.THRESHOLD_AUTO
• blackOnWhite - Trace dark areas on light background or vice versa
  • Default: true
• color - Fill color for the traced paths
  • Default: 'auto'
• background - Background color
  • Default: 'transparent'
• width / height - Output dimensions
  • Default: Original dimensions

Posterizer Parameters

Includes all Potrace parameters plus:

• steps - Number of color levels or specific thresholds
  • Can be a number (2-255) or an array of threshold values
  • Default: Automatic (3 or 4 levels)
• fillStrategy - How colors are selected for each level
  • Options: 'dominant', 'mean', 'median', 'spread'
  • Default: 'dominant'
• rangeDistribution - How color ranges are distributed
  • Options: 'auto', 'equal'
  • Default: 'auto'

Performance Notes

• With default configuration, posterization with 4+ thresholds can take 3-5 seconds on an average laptop due to the automatic thresholding algorithm.
• For better performance, consider:
  • Explicitly limiting steps to 3
  • Pre-resizing large images
  • Increasing turdSize to remove small details
  • Using threshold with a fixed value instead of automatic detection

Credits

• node-potrace - for the inspiration of this project
• Peter Selinger - for the original Potrace tool and algorithm
• @kilobtye - for the javascript port

Testing

bun test

Documentation

For more detailed documentation, examples, and API references, check out our documentation website.

Changelog

Please see our releases page for more information on what has changed recently.

Contributing

Please see CONTRIBUTING for details.

Community

For help, discussion about best practices, or any other conversation that would benefit from being searchable:

Discussions on GitHub

For casual chit-chat with others using this package:

Join the Stacks Discord Server

Postcardware

"Software that is free, but hopes for a postcard." We love receiving postcards from around the world showing where Stacks is being used! We showcase them on our website too.

Our address: Stacks.js, 12665 Village Ln #2306, Playa Vista, CA 90094, United States 🌎

Sponsors

We would like to extend our thanks to the following sponsors for funding Stacks development. If you are interested in becoming a sponsor, please reach out to us.

• JetBrains
• The Solana Foundation

License

The MIT License (MIT). Please see LICENSE for more information.

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