Digital Image Watermark Algorithm in the Curvelet Domain

Watermark is a new effective digital copyright protection method and data security technology. In this paper, a digital image watermark algorithm operating in the curvelet domain is proposed. Unequally-Spaced Fast Fourier Transforms (USFFT) is employed to implement Fast Discrete Curvelet Transforms (FDCT ) to transform the digital image to the curvelet domain. The following three factors are considered when embedding the watermark in the curvelet domain: (1) the scale distribution of the curvelet coefficients; (2) the variation of high frequency components and low frequency components have different effects on HVS; (3) the impact of the variation of the curvelet coefficients on the robustness of the watermark. Combining these factors with the basic watermark algorithm, we choose the proper position to embed the watermark. The experimental results demonstrate a fine unification of robustness and invisibility and shows advantages over watermark algorithm in the ridgelet domain concerning the two aspects.