README.md

msg2img

A JavaScript browser module for encoding arbitrary data into a PNG image.

It uses HTML5 canvas elements to draw images onto. However, the encoding and decoding takes place without attaching any elements to the DOM, so the whole process is completely invisible to the user.

Build

NOTE: The module in msg2img.js is ready to be used in RequireJS environments. If you want to use it without an AMD capable system, use the msg2img_standalone.js file and load it via <script> tag.

The standalone module was built using browserify as follows:

npm install -g browserify
browserify -e msg2img.js -s msg2img -o msg2img_standalone.js

Usage

Please note that the encode function takes an ArrayBuffer object and returns the data URL of the generated PNG image. The decode function works just the other way around.

var msg2img = require("msg2img");
var msg = "Hello there, I am in the image!";

// Encode
var msgArr16 = new Uint16Array(msg.length);
for (var i = 0; i < msg.length; i ++)
  msgArr16[i] = msg.charCodeAt(i);
var imgDataURL = msg2img.encode(msgArr16.buffer);

// Decode
msgArr16 = new Uint16Array(msg2img.decode(imgDataURL));
msg = String.fromCharCode.apply(null, msgArr16);

Tests

Coming soon. For now, just read the sources, they are short and easy to understand.