Stealth Watermark Editor

A wasm pack for embedding and reading stealth watermarks in pictures' alpha channels, inspired by techniques discussed in NovelAI's GitHub repo.

Installation

npm install stealth-watermark-editor

Usage

Below are examples of how to embed and decode information into/from an image's alpha channel:

Embedding Watermark

import init, { embed_stealth_watermark } from 'stealth-watermark-editor';

// Initialize the WASM module only once
await init();

try {
    const imgSrc = 'path/to/image.png'; // Path to the image file
    const metadata = '{"Description": "JSON metadata"}'; // Metadata to embed
    const response = await fetch(imgSrc);
    const imageBuffer = await response.arrayBuffer();

    const watermarkedImage = await embed_stealth_watermark(new Uint8Array(imageBuffer), metadata);
    console.log('Watermark embedded successfully');
} catch (error) {
    console.error('Failed to embed watermark:', error);
}

Decoding Watermark

import init, { decode_stealth_watermark } from 'stealth-watermark-editor';

// Initialize the WASM module only once
await init();

try {
    const response = await fetch('path/to/watermarked_image.png');
    const imageBuffer = await response.arrayBuffer();
    const result = await decode_stealth_watermark(new Uint8Array(imageBuffer));
    console.log('Decoded Metadata:', result);
} catch (error) {
    console.error('Failed to decode watermark:', error);
}

API Reference

• embed_stealth_watermark(imageBytes: Uint8Array, metadata: string): Promise<Uint8Array>

  • Parameters:
    • imageBytes - A Uint8Array containing the bytes of the image.
    • metadata - A string containing the metadata to embed.
  • Returns: A Uint8Array containing the bytes of the image with embedded watermark.
  • Throws: An error if the watermark cannot be embedded.

• decode_stealth_watermark(imageBytes: Uint8Array): Promise<string>

  • Parameters:
    • imageBytes - A Uint8Array containing the bytes of the watermarked image.
  • Returns: A string containing the decoded information.
  • Throws: An error if the watermark cannot be decoded.

Supported Image Formats

The functions support images with an alpha channel such as .png and .webp, as long as Rust's image library can decode them.