htj2k-js

High-Throughput JPEG 2000 (HTJ2K) decoder for Node.js and browser.

Note

This effort is a work-in-progress and should not be used for production purposes.

Install

Node.js

npm install htj2k-js

Browser

<script type="text/javascript" src="https://unpkg.com/htj2k-js"></script>

Build

npm install
npm run build

Features

• Decodes HTJ2K raw codestreams (.j2c, .jpc) and boxed files (.jp2, .jpx, .jph).
• Supports both lossless (reversible, 5/3 LeGall wavelet) and lossy (irreversible, CDF 9/7 wavelet) compression.
• Handles grayscale and color (RGB) images, 8 and 16 bits per component, with signed and unsigned pixel values.
• Supports all five JPEG 2000 progression orders: LRCP, RLCP, RPCL, PCRL and CPRL.
• Outputs per-component pixel arrays (Uint8Array, Uint16Array or Int16Array) as well as a convenient RGBA Uint8Array suitable for HTML5 Canvas, WebGL and WebGPU.
• Provides a common bundle for both Node.js and browser.

Usage

Basic decoding

// Import objects in Node.js
const htj2kJs = require('htj2k-js');
const { Decoder } = htj2kJs;

// Import objects in Browser
const { Decoder } = window.htj2kJs;

// Create an ArrayBuffer with the contents of the HTJ2K byte stream.
const decoder = new Decoder(arrayBuffer);

// Read the image header.
const header = decoder.readHeader();

// Image width.
const width = header.width;
// Image height.
const height = header.height;
// Image bit depth.
const bitDepth = header.bitDepth;
// Image signedness.
const signed = header.signed;
// Number of image components.
const numComponents = header.components;

// Decode and render.
const result = decoder.decodeAndRender();

// Rendered per-component pixel arrays (Uint8Array / Uint16Array / Int16Array).
const components = result.components;

Advanced decoding

// Import objects in Node.js
const htj2kJs = require('htj2k-js');
const { Decoder } = htj2kJs;

// Import objects in Browser
const { Decoder } = window.htj2kJs;

// Create decoder options.
const decoderOpts = {
  // Optional flag to enable segment marker logging.
  // If not provided, segment marker logging is disabled.
  logSegmentMarkers: false,
  // Optional flag to enable box logging (JP2/JPH file format).
  // If not provided, box logging is disabled.
  logBoxes: false,
};

// Create an ArrayBuffer with the contents of the HTJ2K byte stream.
const decoder = new Decoder(arrayBuffer, decoderOpts);

// Read the image header.
const header = decoder.readHeader();

// Image width.
const width = header.width;
// Image height.
const height = header.height;
// Image bit depth.
const bitDepth = header.bitDepth;
// Image signedness.
const signed = header.signed;
// Number of image components.
const numComponents = header.components;
// Number of wavelet decomposition levels.
const decompositionLevels = header.decompositionLevels;
// Progression order (e.g. 'LRCP', 'RPCL', 'CPRL', ...).
const progressionOrder = header.progressionOrder;

// Decode and render directly to RGBA.
const result = decoder.decodeAndRenderToRgba();

// RGBA pixel data as a flat Uint8Array (width × height × 4 bytes).
const rgba = result.data;
// Rendered image width.
const renderedWidth = result.width;
// Rendered image height.
const renderedHeight = result.height;

Please check a live example here.

License

htj2k-js is released under the MIT License.