Abstract: Our objective is to find a theoretical watermarking capacity bound of digital images based on domain-specific masking effects. In this paper, we first show the capacity of private watermarking in which the power constraints are not uniform. Then, we apply several domain-specific Human Vision System approximation models to estimate the power constraints and then show the theoretical watermarking capacity of an image in a general noisy environment. Note that we consider all pixels, watermarks and noises are discrete values, which occur in realistic cases.