  Digital watermarking technique has been presented and widely researched to
solve some important issues in the digital world, such as copyright protection,
copy protection and content authentication. Several robust watermarking schemes
based on vector quantization (VQ) have been presented. In this paper, we
present a new digital image watermarking method based on SOFM vector quantizer
for color images. This method utilizes the codebook partition technique in
which the watermark bit is embedded into the selected VQ encoded block. The
main feature of this scheme is that the watermark exists both in VQ compressed
image and in the reconstructed image. The watermark extraction can be performed
without the original image. The watermark is hidden inside the compressed
image, so much transmission time and storage space can be saved when the
compressed data are transmitted over the Internet. Simulation results
demonstrate that the proposed method has robustness against various image
processing operations without sacrificing compression performance and the
computational speed.
