Robust image watermarking against filtering attacks

This paper propose the method that can embed invisibly gray-level watermark of free size if less than original image size by using SVD (singular value decomposition) and is able to maintain a robustness especially against median and low-pass filtering attacks. Against image low-pass filtering, the extracted watermark of 256 /spl times/ 256 size could be kept over 29.36 dB quality when 3 /spl times/ 3 filter window, against median filtering it also could be kept over 34.61 dB quality, and against lossy JPEG compression, over 37.43 dB until 60% quality.