vitallens.js

Estimate vital signs such as heart rate, HRV, and respiratory rate from video in JavaScript.

vitallens.js is the official JavaScript client for the VitalLens API, a service for estimating physiological vital signs like heart rate, respiratory rate, and heart rate variability (HRV) from facial video.

Using a different language or platform? We also have a Python client and iOS app.

Features

• Cross-Platform Compatibility:
  Use vitallens.js in the browser or Node.js.

• Flexible Input Support: Process video files or live streams from a webcam or any MediaStream.

• Multiple Estimation Methods: Choose the method that fits your needs:

  • vitallens: Provides heart rate, respiratory rate, and heart rate variability estimates. (Automatically selects the best available model for your plan. Requires an API key - get one for free on our website)
  • g, chrom, pos: Offer less accurate heart rate estimates. (No API key required.)

• Fast Face Detection & ROI Support:
  Perform rapid face detection when required—or optionally, pass a global region of interest (ROI) to skip detection for even faster processing.

• Pre-Built Web Component Widgets:
  In addition to the core API, vitallens.js provides ready-to-use web components. Use the unified widget (supporting both file and webcam modes) or choose the specialized file-only or webcam-only widget for streamlined integration.

Installation

Node.js

Install vitallens.js via npm or yarn:

npm install vitallens
# or
yarn add vitallens

Then use it as follows:

import { VitalLens } from 'vitallens';
const vl = new VitalLens({ method: 'vitallens', apiKey: 'YOUR_API_KEY' });
const result = await vl.processVideoFile(myVideoFile);
console.log(result);

Browser

For browser usage, you can either bundle vitallens.js with your project or load it directly from a CDN. In addition to the core API, vitallens.js also provides pre-built web component widgets. We offer three variants:

• Unified Widget: Supports both file and webcam modes with mode toggles.
• File-Only Widget: For processing video files only.
• Webcam-Only Widget: For live webcam streaming only.

For example, using jsDelivr:

<!-- Latest version -->
<script src="https://cdn.jsdelivr.net/npm/vitallens/dist/vitallens.browser.js"></script>

<!-- Or pin a specific version -->
<script src="https://cdn.jsdelivr.net/npm/vitallens@0.2.0/dist/vitallens.browser.js"></script>

<!-- Use with core API -->
<script>
  // vitallens.js is exposed as a global, for example as window.VitalLens.
  const vl = new VitalLens({ method: 'vitallens', apiKey: 'YOUR_API_KEY' });
  // Suppose myMediaStream and myVideoElement are defined:
  vl.addVideoStream(myMediaStream, myVideoElement);
  vl.addEventListener('vitals', (data) => console.log(data));
  vl.startVideoStream();
</script>

<!-- Or use our widget -->
<vitallens-widget api-key="YOUR_API_KEY"></vitallens-widget>

<!-- Or, to use a specialized widget: -->
<!-- File-only widget -->
<vitallens-file-widget api-key="YOUR_API_KEY"></vitallens-file-widget>

<!-- Webcam-only widget -->
<vitallens-webcam-widget api-key="YOUR_API_KEY"></vitallens-webcam-widget>

Alternatively, you can use unpkg:

<script src="https://unpkg.com/vitallens/dist/vitallens.browser.js"></script>

Or Skypack if you prefer ES modules:

<script type="module">
  import { VitalLens } from 'https://cdn.skypack.dev/vitallens';
  // Continue as above…
</script>

How to use

Configuring VitalLens

When creating a new VitalLens instance, you can configure various options:

The default value for waveformMode is windowed if a stream is being analyzed, and complete if a file is being processed.

Methods

You can choose from several rPPG methods:

• vitallens: The recommended method. Uses the VitalLens API and automatically selects the best model for your API key (e.g., VitalLens 2.0 with HRV support)
• vitallens-2.0: Forces the use of the VitalLens 2.0 model.
• vitallens-1.0: Forces the use of the VitalLens 1.0 model.
• pos, chrom, g: Classic rPPG algorithms that run locally and do not require and API key.

Understanding the results

When analyzing a video stream

When analyzing a video stream, VitalLens returns estimation results continuously. Each returned estimation result contains the following vital signs:

When analyzing a video file

When analyzing a video file, VitalLens returns one estimation result for the entire file, containing:

The library returns vital sign estimates in a structured object. vitallens.js is designed to process only a single face — so you always receive a single result object with the following structure:

export interface VitalLensResult {
  face: {
    // Detected face coordinates for each frame, formatted as [x0, y0, x1, y1].
    coordinates: Array<[number, number, number, number]>;
    // Confidence values for the face per frame.
    confidence: number[];
    // An explanatory note regarding the face detection.
    note: string;
  };
  vital_signs: {
    // Estimated global heart rate.
    heart_rate: {
      // Estimated heart rate value.
      value: number;
      // Unit of the heart rate value.
      unit: string;
      // Overall confidence of the heart rate estimation.
      confidence: number;
      // An explanatory note regarding the estimation.
      note: string;
    };
    // Other vitals...
  };
  // A list of timestamps (one per processed frame).
  time: number[];
  // The frames per second (fps) of the input video.
  fps: number;
  // The effective fps used for inference.
  estFps: number;
  // A message providing additional information about the estimation.
  message: string;
}

Examples

Before running any of the examples, make sure to build the project by executing:

npm run build

Also, note that each example requires an API key. Replace YOUR_API_KEY with your actual API key when running the examples.

• Browser Unified Widget:
  examples/browser/widget.html
  To run this example, execute:

  API_KEY=YOUR_API_KEY npm run start:browser

• Browser File Input Widget:
  examples/browser/file_widget.html
  To run this example, execute:

  API_KEY=YOUR_API_KEY npm run start:browser-file

• Browser File Input Minimal:
  examples/browser/file_minimal.html
  To run this example, execute:

  API_KEY=YOUR_API_KEY npm run start:browser-file-minimal

• Browser Webcam Input Widget:
  examples/browser/webcam_widget.html
  To run this example, execute:

  API_KEY=YOUR_API_KEY npm run start:browser-webcam

• Browser Webcam Input Minimal:
  examples/browser/webcam_minimal.html
  To run this example, execute:

  API_KEY=YOUR_API_KEY npm run start:browser-webcam-minimal

• Node File Processing:
  examples/node/file.js
  To run this example, execute:

  API_KEY=YOUR_API_KEY npm run start:node-file

Try opening the HTML examples in your browser or running the Node script to see vitallens.js in action.

Troubleshooting

• Error in Chrome: Refused to cross-origin redirects... This error occurs for some browsers when opening the HTML file directly from your computer, because browser security policies prevent advanced features from running in HTML files opened directly from your computer. Solution: Serve your HTML file from a local web server. In your file's directory, run:

  npx serve

• When to Use the Self-Contained Library Use the self-contained library if your app must run in an environment that blocks requests to public CDNs (like an offline app or behind a corporate firewall). Warning: This file is large and will significantly slow initial page load.

  <script src="https://cdn.jsdelivr.net/npm/vitallens@0.2.0/dist/vitallens.browser.selfcontained.js"></script>

Securing your API Key

For security reasons, we recommend that you do not expose your API key directly in client-side code. There are two primary approaches to secure your API key:

1. Run Everything on your Server

If you are building a server-side application using Node.js, your API key remains securely on your server. Simply call the API directly from your backend code without exposing your credentials.

2. Use a Proxy Server for Client-Side Code

If you need to use vitallens.js in a browser, you can set up a proxy server. The proxy server receives requests from the client, attaches your API key (stored securely on the server), and forwards the request to the VitalLens API. This way, the API key is never exposed to the client.

Our client library supports this by accepting a proxyUrl option. For example:

import { VitalLens } from 'vitallens';
const vl = new VitalLens({
  method: 'vitallens',
  proxyUrl: 'https://your-proxy-server.com/api' // URL to your deployed proxy server
});

Or when using one of our widgets:

<vitallens-widget proxy-url="https://your-proxy-server.com/api"></vitallens-widget>

Sample Proxy Server Implementation

Below is a simple Node.js/Express proxy server implementation that you can use as a starting point:

const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');

const app = express();
const PORT = process.env.PORT || 3000;

// Securely store your API key in an environment variable
const API_KEY = process.env.VITALLENS_API_KEY;
const VITALLENS_ENDPOINT = 'https://api.rouast.com/vitallens-v3/file';

app.use(bodyParser.json({ limit: '10mb' }));

// Enable CORS for your allowed domain.
app.use(cors({
  origin: 'http://example.com', // Your allowed domain
  methods: ['GET', 'POST', 'OPTIONS'],
  allowedHeaders: ['Content-Type', 'Authorization']
}));

app.post('/', async (req, res) => {
  try {
    const response = await fetch(VITALLENS_ENDPOINT, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'x-api-key': API_KEY,
      },
      body: JSON.stringify(req.body),
    });
    const data = await response.text();
    res.status(response.status).send(data);
  } catch (error) {
    console.error('Proxy error:', error);
    res.status(500).send('Internal server error');
  }
});

app.listen(PORT, () => {
  console.log(`Proxy server listening on port ${PORT}`);
});

You can deploy this proxy server on any Node.js hosting platform (such as Heroku, Vercel, or your own server) and then set the URL as the proxyUrl in your VitalLens client configuration.

Development

Building the Library

To build the project from source, run:

npm run build

This compiles the TypeScript source and bundles the output for Node (both ESM and CommonJS), and the browser.

Running Tests

Execute the test suite with:

npm run test

For environment-specific tests, you can use:

npm run test:browser
npm run test:node
npm run test:browser-integration
npm run test:node-integration

Run specific tests:

npx jest test/core/VitalLens.browser.test.ts

Linting

Lint the code using:

npm run lint

Disclaimer

Important: vitallens.js provides vital sign estimates for general wellness purposes only. It is not intended for medical use. Always consult a healthcare professional for any medical concerns or precise clinical measurements.

Please review our Terms of Service and Privacy Policy for more details.

License

This project is licensed under the MIT License.