Tree Energy Differentiation (TED) based wavelet watermarking for digital images

In this paper, we present a novel differential energy watermarking algorithm called Tree Energy Differentiation (TED) based on the wavelet tree structure. The wavelet coefficients of the image are divided into disjoint trees called wavelet trees. A wavelet tree consists of 21 coefficients and is divided into 6 blocks. One watermark bit is embedded into one wavelet tree using the energy differentiation between coefficients of each block. In addition, the contrast sensitive function (CSF) of human visual system is also considered for better weighting in watermarking. Using this approach, we can check each wavelet tree to verify the watermark existence for copyright protection and ownership verification. The experimental results demonstrate the effectiveness of TED algorithm in terms of robustness and imperceptibility of watermarking.