stegomark

A package for watermarking images with images with LSB. (currently only works with pngs)

How to use

var stego = require('stegomark')
stego.write("in.png", "write.png", "out.png", {
  "callback": function () {
    stego.read("out.png", "extracted.png")
  }
})

Functions

stego.write(in_path, watermark_path, out_path[, options])
stego.read(in_path, extracted_path[, options])

Options

• callback: to be called when the output image write is finished
• squeeze_protection: only on write - integer - the higher this integer, the more resistance to resizing

How it works

The image watermark is rounded to 3-bit color - enough to fit in the LSBs of R, G, and B

For example, if we wanted to watermark the pixel with color FEB101 (orange) with another pixel of color FF006E (pink), the program would:

1. Round the color to be watermarked Essentialy, it divides the value of each color channel by 255, rounds to the nearest integer, and reconcatenates. This process results in a 3 bit color of 100, which expanded to 24 bit is FF0000 i.e. red
2. Take the 3 bit color and put it in the lowest bits of each channel of the original image. This results in a new color of FFB000 (very slightly different orange)
3. Repeat for all the watermark pixels

Reading does this in reverse.

Why is this better?

1. In other LSB implementations, data stored in individual pixels is dependent on data from other pixels. However, by sacrificing color quality, we can store small, independent groups of data
2. (my opinion) I like the visual system more - rather than extracting a cryptic message, one can show the message in a visual form.

Example!

The input image below:

Was watermarked with this and a squeeze protection of 5:

And created this output image:

That had this data:

Testing against squeezing

I squeezed the output image in paint.net to get this:

But I was still able to extract this image: