Our objective is to nd a theoretical watermarking capac-ity bound of digital images based on domain-speci c masking e ects. In this paper, we rst show the capacity of private wa-termarking in which the power constraints are not uniform. Then, we apply several domain-speci c Human Vision Sys-tem 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 con-sider all pixels, watermarks and noises are discrete values, which occur in realistic cases. 1