Image watermarking scheme based on 3-D DCT

Robust watermarking techniques are always used for copyright and ownership assertion purposes. And many watermark embedding schemes in transform domain are proposed, such as 2-D DFT, 2-D DCT, 2-D DWT, 3-D DCT and 3-D DWT. Among them, the former three ones are used to transform image data, and the latter two ones are used to transform video data or 3-D image data. In this paper, we present an image watermarking scheme based on 3-D DCT. A gray-level image is decomposed into a 3-D sub-image sequence by sub-sample of zigzag scanning order that is transformed using block-based 3-D DCT. Simultaneously, we prove that the distribution of 3-D DCT AC coefficients follows the generalized Gaussian density function using the distribution relative entropy theory. To satisfy the balance between the robustness and the imperceptivity, a 3-D HVS model is improved to adjust the embedding strength. In watermark detecting, the optimum detector is used to implement the blind detection. It is shown in our experiments that the scheme is strongly robust against various attacks.