Blind Watermarking Scheme Based on Rdwt-dct for Color Images

In Digital era sharing of images have become very common and raises the risk of using it for unethical and fraudulent purposes with the help of manipulation tools. Digital image watermarking is one way to protect the digital information (text, images, audio, and video) from fraudulent manipulations. Digital Image Watermarking is a process of implanting data in the original image for authentication. In this paper we are providing one such watermarking scheme for color images. The proposed method is designed to be robust for common attacks with the aid of redundant discrete wavelet transform (RDWT) and discrete cosine transform (DCT) properties. After applying two levels RDWT decomposition to the blue channel of cover image, we apply DCT to HH_LL subband i.e. 2 level decomposed coefficient of HH band and to the watermark. Divided the HH_LL sub band into 4x4 subblocks and DCT coefficients of the last subblock of the cover image are replaced with the DCT coefficients of watermark. Inverse DCT and inverse RDWT is performed to get watermarked image. The performance of the proposed technique is measured using the parameters PSNR and NCC. Keywords— RDWT, DCT, PSNR, NCC