Digital image watermarking employing codebook in vector quantisation

Two simple watermarking techniques for a digital image are proposed. The methods employ a codebook in vector quantisation, and can extract watermark information from a watermarked image without an original image. Simulation results show that when the codebook of a larger size is used, a reconstructed image with a watermark has better quality than that without a watermark, and, for one of the proposed methods, a watermark size and the percentage of 0 bit contained in a watermark have almost no effect on PSNR for a reconstructed image.