A VQ-DCT Scheme for Grayscale Image Watermarking

Abstract

paper, a hybrid watermarking scheme, that employs both DCT and VQ, has been presented. The authors have proposed a modification of the conventional LBG algorithm in this paper for designing the codebook to be used subsequently for compressing the image employing VQ. The watermark/logo is embedded in the constructed codebook after suitable DCT operations. The compression and reconstruction of the cover image employs the modified embedded codebook. The indirect mechanism of embedding the watermark and the hybrid combination of VQ and DCT make the entire watermarking scheme reasonably robust with respect to various types of common attacks which include intensity modification in real domain, modification in transformed domain namely JPEG compression etc. The method has been implemented and tested on a number of example images. We have also tested the robustness of authenticating capability of the scheme both qualitatively and quantitatively for various types of attacks.