Abstract:The paper presents an imperceptible and robust digital watermarking algorithm using a combination of the DWT-DCT , which improves the robustness via using new embedding strategy. Apply 4-level DWT to the host image. Then, DCT transform of each directional middle frequencies DWT subband is computed; A binary watermarked logo is coded by Run-Length Code(RLC);The watermark bits are embedded in the coefficients of the DCT block based on the energy of each corresponding to coefficient in the highest level selected using the value of RLC. Performance evaluation show that the proposed scheme is invisible and robust against common image manipulations like JPEG compression, noise adding, sharpening, filtering. I IntroductionImage watermarking is the process of embedding the ownership information into host data so that intellectual copyrights can be identified. Along with the rapid growth of novel watermarking schemes, various attacking attempts have also been developed to destroy watermarking [1] . Such attacks as median filtering, compression, noise, and cropping, can easily make most of existing watermarking schemes ineffective. This is mainly due to the fact that slight manipulation for the marked image could desynchronizes the location of the watermark and causes incorrect watermark detection. In other words, the detection or extraction of the watermark requires a synchronization step to locate the embedded mark in the content. Recent contributions have shown that image adaptive watermarking schemes can be successfully implemented by changing some coefficients of transform domain. Commonly used frequency-domain watermarking schemes are the discrete cosine transform (DCT) [2] -based, the discrete wavelet transform (DWT) [3,4] -based and Discrete Fourier Transform (DFT) [5] -based. DWT typically provide higher imperceptibility and are much more robust to image process due to its excellent spatial localization and multi-resolution characteristics, which are similar to the theoretical models of the human visual system. Further performance improvements in DWT-based digital image watermarking algorithms could be obtained by combining DWT with DCT [6,7] .In this paper, we will propose a digital image watermarking algorithm based on DWT-DCT domain and RLC. Encoding binary watermark logo by Run-Length Code;the binary watermark image are embedded in the low-middle frequency coefficients of selected DCT blocks according to the RLC. The idea of applying RLC is based on the fact that RLC of binary watermarking image could favor the orientation of embedded watermarking imformation, so that effective watermarking approaches could acquire. II Theory A.Run Length CodeRun-length code (RLC) is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. This is most useful on data that contains many such runs: for example, simple graphic images such as icons, l...