An improved DCT based zero-watermarking algorithm for text image

An improved zero-watermarking algorithm, which solving the contradiction between the watermark embedding capacity of and invisibility, was proposed. The zero-watermarking algorithm needn´t to modify the carrier; so many watermarking methods can be used and without the need to consider the embedding capacity, and robustness is better than the normal watermarking algorithm. The steps of proposed zero-watermarking algorithm are as follows: first, the text carrier is translated into the corresponding binary image, then use DCT combined with the logistic mapping to construct zero-watermark, the similarity criteria was used for the watermark detection. After many attacking experiments, performance of the algorithm shows that the robustness, invisibility and the watermark capacity of the algorithm, can meet the requirements of practical need.