Good library for Digital watermarking

Question

Can somebody help me, to find a library, or a detailed description of algorithm, that could embed a Digital watermark(invisible watermark, just a kind of steganography) to a jp

Answer 1

Pistache is right in what he told you regarding the watermarking implementation algorithms. I will try to help you by showing one algorithm for the given requirements.

Before explaining you the algorithms first I guess that the distinction between the JPG and PNG formats should be done.

1. JPEG is a lossy format, i.e, the images are susceptible to compression that could remove the watermark. When you open an image for manipulation purposes and you save it, upon the writing procedure, a compression is made by using DCT filtering that removes some important components of the image.
2. On the other hand, PNG format is lossless, and that means that images are not susceptible to such kind of compression when stored after manipulation.

As a matter of fact, JPEG is used as a watermarking scheme attack due to its compressing characteristic that could remove the watermark if an attacker performed the compression.

Now that you know the difference between both formats, I can tell you a suitable algorithm resistant to the attacks that you mentioned.

Regarding methods to embed a watermark message for PNG files you can use the histogram embedding method. The histogram embedding method changes values on the histogram by changing the values of the neighbor bins. For example imagine that you have a PNG image in grayscale. Therefore, you'll have only one channel for embedding and that means that you have one histogram with 256 bins. By selecting the neighbor bins x and x+1, you change the values of x and x+1 by moving the pixels with the bright x to x+1 or the other way around, so that (x/(x+1))>T for embedding a '1' or ((x+1)/x)>T for embedding a '0'.

You can repeat the same procedure for the whole histogram length and therefore you can embed in the best case up to 128bits. However this payload is less than what you asked. Therefore I suggest you to split the image into parts, for example blocks, and if you split one image into 4 components you'd be able to embed in the best case up to 512 bits which means 64 bytes. This method although is very, susceptible to filtering and compression if applied straight in the space domain. Therefore, I suggest you to compute before the DWT of the image and use its low-frequency sub-band. This will provide you better transparency and robustness increased for the warping, resizing etc attacks and compression or filtering as well.

There are other approaches such as LPM (Log Polar Maps) but they are very complex to implement and I think for your case this approach would be fine.

I can suggest you two papers, the first is:

Watermarking digital image and video data. A state-of-the-art overview

This paper will give you some basic notions of watermarking and explain more in detail the LSB algorithm. And the second paper is:

Real-Time Compressed- Domain Video Watermarking Resistance to Geometric Distortions

This paper will explain the algorithm that I just explained now.

Cheers,