Abstract: In this paper we propose, a blind digital image watermarking algorithm based on combined DWT-DCT transformation with low frequency watermarking. The watermark embedding is carried out by modifying the wavelets coefficients of carefully selected DWT sub-band of a host image after two levels of DWT decomposition, followed by the application of the block based DCT transform on the selected sub-band. Watermark embedding is done using low frequency coefficients of each selected 44 DCT block. The watermarked host image is exposed to several watermark attacks. Experimental results demonstrate that the proposed algorithm is able to withstand a variety of common signal processing and geometric attacks.

Keywords: Discrete Cosine Transform, Digital Image Watermarking, Discrete Wavelet Transform, PSNR.