Watermark survival chance (WSC) concept for improving watermark robustness against JPEG compression

This paper presents the new concept of watermark survival chance (WSC) for improving watermark robustness. WSC provides a robustness measure for an image feature (e.g. a discrete wavelet transform (DWT) coefficient) when used for watermark embedding, and thus can provide the watermark designer with prior knowledge on robust image features. As an illustrative example, we study additive spread spectrum watermarking in the DWT domain and consider JPEG compression as the attack. WSC is obtained for each DWT coefficient/subband for different compression ratios. Based on the WSC table for JPEG compression distortion, we suggest that: Wavelet coefficients can be divided into two main categories: block boundary coefficients and block non-boundary coefficients; block boundary coefficients generally are more robust for watermark embedding than block non-boundary coefficients; larger scale wavelet coefficients are generally more robust than smaller scales; a vertical subband is slightly preferred at small and large scales, while a horizontal subband is preferred at a medium scale.