Low Frequency Component-Based Watermarking Scheme using 2D Datamatrix
A robust watermark should be able to withstand most image manipulations such as cropping, additive noise and JPEG type compressions. It should also be able to hold telltale signs of attacks that are unknown to the user. Both of these aims can be fulfilled by embedding two watermarks, one fragile and one robust in different domains where watermarks are not vulnerable to the aforementioned manipulations. It is a well known fact that watermarking of DC components of discrete cosine transform (DCT) stand against JPEG compression. We build on this concept by inserting a watermark in the transform domain to further enhance the robustness. We use a 2D Datamatrix as the watermark as this has error correction capabilities and we show that this can be used to insert data imperceptibly into the host image. A second Datamatrix watermark is embedded in the low pass component of any wavelet decomposition at a specific level only known to the author. This improves the resistance of the watermarking scheme to attack. Our experimental results indicate that these invisible watermarks can carry significant information and are robust to many image manipulations.