CharLS WebAssembly


CharLS WebAssembly is a WebAssembly build of CharLS, a high-performance JPEG-LS codec library. This package provides JavaScript/TypeScript bindings for encoding and decoding JPEG-LS images in both Node.js and browser environments.

This project was originally forked from charls-js, created by Chris Hafey. It has been updated to use Wasm 3.0 and the latest version of CharLS.

Installation

``bash
npm install @team-charls/charls-wasm
`

Quick Start

$3

`javascript
import { createJpegLSDecoder } from '@team-charls/charls-wasm'

// Typical pattern is to re-use decoder instances for better performance.
const decoder = await createJpegLSDecoder()

function decodeImage (sourceBuffer) {
const destinationBuffer = decoder.decode(sourceBuffer)

console.log('Frame info:', decoder.getFrameInfo())
console.log('Interleave mode:', decoder.getInterleaveMode())
console.log('Near lossless:', decoder.getNearLossless())

return destinationBuffer
}
`

$3

`javascript
import { createJpegLSEncoder } from '@team-charls/charls-wasm'

// Typical pattern is to re-use encoder instances for better performance.
const encoder = await createJpegLSEncoder()

function encodeImageLossless (pixelBuffer, frameInfo) {
const destinationBuffer = encoder.encode(pixelBuffer,
frameInfo.width,
frameInfo.height,
frameInfo.bitsPerSample,
frameInfo.componentCount,
0, // Interleave mode (0 = none, 1 = line, 2 = sample)
0, // Encoding options bitmask (0=none, 1=evenSize, 2=includeVersion, 4=includePCParametersJAI)
0 // NEAR parameter (0 = lossless, >0 = near-lossless)
)

return destinationBuffer
}
`

API Reference

$3

- createJpegLSDecoder() - Creates a new decoder instance (async)
- createJpegLSEncoder() - Creates a new encoder instance (async)
- initializeModule() - Explicitly initialize the WASM module (optional, called automatically)

$3

- JpegLSDecoder - Decoder class for advanced usage
- JpegLSEncoder - Encoder class for advanced usage
- JpegLSError` - Custom error class for JPEG-LS operations

Supported Platforms

All environments that can run Wasm 3.0 modules are supported:

- Browsers: Chrome/Edge 137+, Firefox 131+, Safari 26.2+
- Node.js: 18.0+

Examples

For complete examples, see:
- Browser example
- Node.js example

Resources

- GitHub Repository
- CharLS C++ Library
- Live Demo
- API Documentation

License

BSD-3-Clause - See LICENSE.md