Combined-transforms-based robust colour image watermarking schemes

摘要

In this paper, two combined transforms are explored for colour image watermarking namely Discrete Wavelet Transform-Fan Beam Transform (DWT-FBT); Spatio-Chromatic Discrete Fourier Transform-Fan Beam Transform (SCDFT-FBT). In the first approach, a host image is subject to DWT and FBT is applied after careful selection of the suitable band of wavelet coefficients. Watermarking is done by altering the fan beam transformed coefficients. Hence, this domain is termed as DWT-FBT domain. In the second approach, watermarking is done on selected SCDFT coefficients that are transformed using FBT and hence termed as SCDFT-FBT. The DWT-FBT domain shows superior performance than SCDFT-FBT domain in its resistance to compression, cropping, colour conversion and rotation. Results of the proposed combined transforms are compared with the two existing DWT-DCT domain watermarking schemes to show their effectiveness.