Human visual system models in Digital Watermarking

In this paper, a review of Human Visual System (HVS) based Digital Watermarking schemes are presented with their mathematical model. The HVS system exploits several properties of human eyes in spatial as well as frequency domain. In spatial domain, Just Noticeable Difference (JND) along with Luminance Sensitivity (LS), Contrast Masking (CM) and some other masking effects are playing important role. On the other hand, HVS models in transform domain are dependent on various sub-band features and also incorporating to Contrast Sensitivity Function (CSF) with Luminance Adaption (LA) and Contrast Masking (CM) effects. Apart from these, HVS models are also composed of contrast threshold with a function of spatial frequency and eccentricity of human eyes. In addition, Noise Visibility Function (NVF) is also discussed in this paper.