Multipurpose Watermarking Scheme using Essentially Non-Oscillatory Point-Value Decomposition
27 Jan 2009-Proceedings of SPIE (International Society for Optics and Photonics)-Vol. 7248, pp 158-169
TL;DR: The meaning of the word multipurpose is to make the proposed scheme as single watermarking scheme (SWS) or multiple watermarked scheme (MWS) according to the authors' requirement and convenience.
Abstract: In this paper, a multipurpose watermarking scheme is proposed. The meaning of the word multipurpose is to make the proposed scheme as single watermarking scheme (SWS) or multiple watermarking scheme (MWS)
according to our requirement and convenience. We first segment the host image into blocks by means of Hilbert space filling curve and based on amount of DCT energy in the blocks, the threshold values are selected which make proposed scheme multipurpose. For embedding of n watermarks (n - 1) thresholds are selected. If the
amount of DCT energy of the block is less than the threshold value then ENOPV decomposition is performed and watermark is embedded in either low or high or all frequency sub-bands by modifying the singular values. If the amount of DCT energy of the block is greater than the threshold value then embedding is done by modifying
the singular values. This process of embedding through ENOPV-SVD and SVD is applied alternatively to all (n - 1) threshold values. Finally, modified blocks are mapped back to their original positions using inverse Hilbert space filling curve to get the watermarked image. A reliable extraction process is developed for extracting all
watermarks from attacked image. Experiments are done on different standard gray scale images and robustness is carried out by a variety of attacks.
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Additional excerpts
...f θ = Ufm θ Sfm θ V T fm θ Wj = UWj SWj V T Wj (5)...
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TL;DR: A new approach to mask the watermark according to the characteristics of the human visual system (HVS) is presented, which is accomplished pixel by pixel by taking into account the texture and the luminance content of all the image subbands.
Abstract: A watermarking algorithm operating in the wavelet domain is presented. Performance improvement with respect to existing algorithms is obtained by means of a new approach to mask the watermark according to the characteristics of the human visual system (HVS). In contrast to conventional methods operating in the wavelet domain, masking is accomplished pixel by pixel by taking into account the texture and the luminance content of all the image subbands. The watermark consists of a pseudorandom sequence which is adaptively added to the largest detail bands. As usual, the watermark is detected by computing the correlation between the watermarked coefficients and the watermarking code, and the detection threshold is chosen in such a way that the knowledge of the watermark energy used in the embedding phase is not needed, thus permitting one to adapt it to the image at hand. Experimental results and comparisons with other techniques operating in the wavelet domain prove the effectiveness of the new algorithm.
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"Multipurpose Watermarking Scheme us..." refers background in this paper
...The n − 1 thresholds are given by Tj = Sort ( j ∗ ⌊ Tl n ⌋ ) (4) where Sort(◦) are the sorted DCT energy of blocks, T l is total number of blocks and j = 1, 2, ....
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