A novel video object based watermarking scheme is proposed in this paper, providing copyright protection of the semantic content. To achieve this goal, an adaptive two-dimensional Gaussian model of skin color distribution is initially used in order to detect face and body regions within the initial image. An invariant watermark is then designed and tested against attacks using invariant Hu moments. The proposed algorithms have the advantages of being robust, computationally efficient, and overheads transmitted to the decoder side are very low. Performance of the proposed object based watermarking system is tested under various signal distortions such as JPEG lossy compression, blurring, filtering and cropping, Experimental results on real life images indicate the efficiency and robustness of the proposed scheme.