Three Dimensional Discrete Wavelet Transform Based Robust Multiple Watermarking Algorithm for Spectral Images

Three Dimensional (3-D) imaging is a fast growing technology in the areas of computer graphics, robotics, metrology, medicine and cultural heritage etc. With the development of internet, 3-D contents are easily manipulated, transmitted and widely distributed. Watermarking has been proved to be an efficient technology in copyright protection of multimedia information. In this paper, a novel blind multiple watermarking algorithm for copyright protection of spectral images is presented. Watermarking is based on 3-D Discrete Wavelet Transform (DWT). Dual binary watermarks are proposed to embed in the mid frequency bands of cover image. One level 3-D DWT is applied to the original spectral image and one level 2-D DWT is applied on two binary watermarks. Eigen values of selected subbands of spectral image are modified by the eigen values of selected subbands of two binary watermarks. Inverse SVD (Singular Value Decomposition) and Inverse 3-D DWT is taken on the modified subbands to obtain the watermarked image. During extraction process, two binary watermarks are recovered from the test image with the help of a secret key. An experimental result shows that, the proposed algorithm produces very high imperceptibility and robustness against various types of attacks like low pass filtering, median Filtering, JPEG compression, histogram equalization, cropping, various angles of rotation and addition of noise like Gaussian, Salt &Pepper, Speckle, Poisson etc.