Human Visual System Models in Digital Image Watermarking
P. Foris, D. Levicky · DOAJ (DOAJ: Directory of Open Access Journals) · 2004
In this paper some Human Visual System (HVS) models used in digitalimage watermarking are presented. Four different HVS models, whichexploit various properties of human eye, are described. Two of themoperate in transform domain of Discrete Cosine Transform (DCT) andDiscrete Wavelet Transform (DWT). HVS model in DCT domain consists ofJust Noticeable Difference thresholds for corresponding DCT basisfunctions corrected by luminance sensitivity and self- or neighborhoodcontrast masking. HVS model in DWT domain is based on different HVSsensitivity in various DWT subbands. The third presented HVS model iscomposed of contrast thresholds as a function of spatial frequency andeye's eccentricity. We present also a way of combining these threebasic models to get better tradeoff between conflicting requirements ofdigital watermarks. The fourth HVS model is based on noise visibilityin an image and is described by so called Noise Visibility Function(NVF). The possible ways of exploiting of the described HVS models indigital image watermarking are also briefly discussed.