🎯 arjs-plugin-artoolkit ⚡🕶️

Lightweight WebWorker ARToolKit plugin for AR.js that detects square markers using WebAssembly and ImageBitmap zero-copy transfers, offering an event-driven API for realtime camera input, fast detection, and easy integration. 🔎🎯🚀⚡🧩

Table of Contents

• Features
• Version
• Installation
• Using the ESM build (recommended)
• Using source (development mode)
• Usage
  • Quick Start (copy-paste)
  • Register and enable
  • Events
  • Sending frames
  • Loading a pattern marker
• Examples
• API Reference
• Troubleshooting

Features ✨🧭

• 🧠 Web Worker-based detection — marker detection runs off the main thread (Browser Module Worker)
• 🖼️ ImageBitmap support — zero-copy frame transfer for efficient camera frames
• 🧩 ARToolKit integration — square pattern markers (patt files)
• ⚡ Event-driven API — markerFound / markerUpdated / markerLost + raw getMarker events
• 🔍 Confidence filtering — only forwards PATTERN_MARKER events above minConfidence

Version 🏷️

The plugin exposes its build-time version both as a constant and on each instance:

import {
  ArtoolkitPlugin,
  ARTOOLKIT_PLUGIN_VERSION,
} from "@ar-js-org/arjs-plugin-artoolkit";

console.log("Build version:", ARTOOLKIT_PLUGIN_VERSION); // e.g. 0.1.0 or 'unknown'
const plugin = new ArtoolkitPlugin();
console.log("Instance version:", plugin.version);

If the build-time define is missing (for example when using raw source or some test runners), the version falls back to 'unknown'.

Installation 📦

# Attention: package may not be published yet
npm install @ar-js-org/arjs-plugin-artoolkit

Using the ESM build (recommended) 🚀

When you import the built ESM bundle from dist/, the worker and ARToolKit are already bundled and referenced correctly. You do NOT need to pass artoolkitModuleUrl.

Example:

<script type="module">
  import { ArtoolkitPlugin } from '/dist/arjs-plugin-artoolkit.es.js';

  const engine = { eventBus: /* your event bus */ };

  const plugin = new ArtoolkitPlugin({
    worker: true,
    cameraParametersUrl: '/path/to/camera_para.dat',
    minConfidence: 0.6
  });

  await plugin.init(engine);
  await plugin.enable();
  console.log('Plugin version:', plugin.version);
</script>

Serving notes:

• Serve from a web server so /dist assets resolve. The build is configured with base: './', so the worker asset is referenced relative to the ESM file (e.g., /dist/assets/worker-*.js).
• In your own apps, place dist/ where you serve static assets and import the ESM with the appropriate path (absolute or relative).

Using source (development mode) 🛠️

If you develop against src/ (not the built dist/), the worker will attempt to dynamically import ARToolKit. In that case, you must provide a valid artoolkitModuleUrl (for example a direct path to the UMD or ESM build) or ensure your dev server can resolve @ar-js-org/artoolkit5-js as an ES module. Browser module loading issues may occur if the module is not properly served or is not an ES module.

const plugin = new ArtoolkitPlugin({
  worker: true,
  artoolkitModuleUrl: '/node_modules/@ar-js-org/artoolkit5-js/dist/ARToolkit.js', // provide when using src/
  cameraParametersUrl: '/path/to/camera_para.dat',
  wasmBaseUrl: '/node_modules/@ar-js-org/artoolkit5-js/dist/', // optional; if your build requires it
  minConfidence: 0.6,
});
console.log('Plugin version:', plugin.version);

CDN fallback (for source/dev):

• Set artoolkitModuleUrl to a CDN ESM endpoint (e.g., jsDelivr/UNPKG) for @ar-js-org/artoolkit5-js.

Notes:

• The previous loader.js and manual WASM placement flow is no longer used.
• In the dist/ build, ARToolKit is bundled and artoolkitModuleUrl is NOT needed.

Usage 🧩

Quick Start (copy-paste) ⚡

import { ArtoolkitPlugin } from "@ar-js-org/arjs-plugin-artoolkit";

// Minimal event bus stub
const eventBus = {
  _h: new Map(),
  on(e, h) {
    if (!this._h.has(e)) this._h.set(e, []);
    this._h.get(e).push(h);
  },
  emit(e, p) {
    (this._h.get(e) || []).forEach((fn) => {
      try {
        fn(p);
      } catch (err) {
        console.error(err);
      }
    });
  },
};
const engine = { eventBus };

const plugin = new ArtoolkitPlugin({ worker: true, minConfidence: 0.6 });
await plugin.init(engine);
await plugin.enable();
console.log("Version:", plugin.version);

// Load a marker (size is world units)
await plugin.loadMarker("/examples/simple-marker/data/patt.hiro", 1);

eventBus.on("ar:markerFound", (m) => console.log("FOUND", m.id));
eventBus.on("ar:markerUpdated", (m) => console.log("UPDATED", m.id));
eventBus.on("ar:markerLost", (m) => console.log("LOST", m.id));

Register and enable ✅

import { ArtoolkitPlugin } from "@ar-js-org/arjs-plugin-artoolkit";

const plugin = new ArtoolkitPlugin({
  worker: true,
  lostThreshold: 5, // frames before a marker is considered lost
  frameDurationMs: 100, // expected ms per frame (affects lost timing)
  // artoolkitModuleUrl: '/node_modules/@ar-js-org/artoolkit5-js/dist/ARToolkit.js', // Only for src/dev
  cameraParametersUrl: "/data/camera_para.dat",
  minConfidence: 0.6,
});

engine.pluginManager.register("artoolkit", plugin);
await engine.pluginManager.enable("artoolkit");

Events 🔔

The plugin emits the following events on your engine’s event bus:

// Marker first detected
engine.eventBus.on(
  "ar:markerFound",
  ({ id, poseMatrix, confidence, corners }) => {
    // poseMatrix is Float32Array(16)
  },
);

// Marker updated (tracking)
engine.eventBus.on("ar:markerUpdated", (data) => {
  // same shape as markerFound
});

// Marker lost
engine.eventBus.on("ar:markerLost", ({ id }) => {});

// Worker lifecycle
engine.eventBus.on("ar:workerReady", () => {});
engine.eventBus.on("ar:workerError", (error) => {});

// Raw ARToolKit getMarker (filtered: PATTERN_MARKER only, above minConfidence)
engine.eventBus.on("ar:getMarker", (payload) => {
  // payload = { type, matrix: number[16], marker: { idPatt, cfPatt, idMatrix?, cfMatrix?, vertex? } }
});

Sending frames 🎞️

// Create ImageBitmap from a <video> or <canvas>
const imageBitmap = await createImageBitmap(video);

// Emit an engine update; the plugin transfers the ImageBitmap to the worker
engine.eventBus.emit("engine:update", {
  id: frameId,
  timestamp: Date.now(),
  imageBitmap,
  width: imageBitmap.width,
  height: imageBitmap.height,
});

// The ImageBitmap is transferred and cannot be reused; the worker will close it.

Loading a pattern marker 📐

const { markerId, size } = await plugin.loadMarker(
  "/examples/simple-marker/data/patt.hiro",
  1,
);

Examples 🧪

A complete webcam-based example is available under examples/simple-marker/.

Serve from the repository root so that dist/ and example paths resolve:

# From repository root
npx http-server -p 8080
# or
python3 -m http.server 8080

Open:

• http://localhost:8080/examples/simple-marker/index.html

The example demonstrates:

• Webcam capture with getUserMedia
• ImageBitmap creation and frame submission
• Event handling and console output
• Raw ar:getMarker payloads for debugging

API Reference 📚

ArtoolkitPlugin options 🧭

{
  worker?: boolean;            // Enable worker (default: true)
  lostThreshold?: number;      // Frames before 'lost' (default: 5)
  frameDurationMs?: number;    // ms per frame used with lostThreshold (default: 200)
  sweepIntervalMs?: number;    // Lost-sweep interval (default: 100)
  artoolkitModuleUrl?: string; // Only needed when using source/dev; not needed for dist build
  cameraParametersUrl?: string;// Camera params file URL (required unless you rely on a remote default)
  wasmBaseUrl?: string;        // Base URL for ARToolKit assets (optional)
  minConfidence?: number;      // Minimum confidence to forward getMarker (default: 0.6)
}

Methods 🛠️

• async init(core) — initialize with engine core
• async enable() — start worker and subscribe to frames
• async disable() — stop worker and timers
• dispose() — alias for disable
• getMarkerState(markerId) — current tracked state
• async loadMarker(patternUrl: string, size = 1) — load and track a pattern

Troubleshooting 🧰

• Worker asset 404:
  • Ensure you import the ESM from /dist/arjs-plugin-artoolkit.es.js and that /dist/assets/worker-*.js is served.
  • The build uses base: './', so worker URLs are relative to the ESM file location.
• “Failed to resolve module specifier” in the Worker (source/dev only):
  • Provide artoolkitModuleUrl or serve /node_modules from your dev server
• Worker not starting:
  • Serve via HTTP/HTTPS; ensure ES modules and Workers are supported
• No detections:
  • Confirm camera started, correct marker pattern, sufficient lighting
  • Adjust minConfidence to reduce/raise filtering
  • Check plugin.version (if 'unknown', ensure build-time define is configured)