lsb-steganography/dist/lib.js

A coomand-line tool for encoding/decoding data via image.

import { writeFile } from "node:fs/promises";
import { Jimp } from "jimp";

//#region src/lib.ts
const MASK_0F = 15;
const MASK_F0 = 240;
const MASK_FF = 255;
async function encode(str, { input }) {
	const textEncoder = new TextEncoder();
	const buffer = textEncoder.encode(str);
	let image;
	let width = 0;
	let height = 0;
	async function getJimpInstance() {
		if (typeof input === "string") return await Jimp.read(input);
		if (input instanceof ArrayBuffer) return Jimp.fromBuffer(input);
	}
	if (input) {
		const jimp = await getJimpInstance();
		if (!jimp) throw new Error("Invalid input");
		const size = jimp.width * jimp.height * 4;
		const pixelApset = Math.sqrt(size / (buffer.length * 2));
		width = Math.ceil(jimp.width / pixelApset);
		height = Math.ceil(jimp.height / pixelApset);
		image = jimp.resize({
			w: width,
			h: height
		});
	} else {
		const Sqrt3Div2 = Math.sqrt(3 / 2);
		width = Math.ceil(Math.sqrt(buffer.length) / Sqrt3Div2);
		height = width;
		image = new Jimp({
			color: 4042322160,
			width,
			height
		});
	}
	for (let i = 0; i < buffer.length; i++) {
		image.bitmap.data[i * 2] = ((image.bitmap.data[i * 2] ?? MASK_FF) & MASK_F0) + (buffer[i] >> 4 & MASK_0F);
		image.bitmap.data[i * 2 + 1] = ((image.bitmap.data[i * 2 + 1] ?? MASK_FF) & MASK_F0) + (buffer[i] & MASK_0F);
	}
	for (let i = 2 * buffer.length; i < width * height * 4; i++) image.bitmap.data[i] = (image.bitmap.data[i] ?? MASK_FF) & MASK_F0;
	return {
		data: image.bitmap.data,
		async writeFile(path) {
			return image.write(`${path}.png`);
		}
	};
}
async function decode(input) {
	const textDecoder = new TextDecoder("utf-8");
	const jimpInput = typeof input === "string" ? await Jimp.read(input) : await Jimp.fromBuffer(input);
	const buffer = jimpInput.bitmap.data;
	const array = new Uint8Array(buffer.length);
	for (let i = 0; i < buffer.length; i += 2) array[i] = ((buffer[i] & MASK_0F) << 4) + (buffer[i + 1] & MASK_0F);
	const data = textDecoder.decode(array);
	return {
		data,
		writeFile(output) {
			return writeFile(data, output);
		}
	};
}

//#endregion
export { decode, encode };