Human visual system based adaptive digital image watermarking

It is known that there is a trade off between the imperceptibility and robustness of a digital watermarking system. Trying to deal with this problem, a new adaptive digital image watermarking method is proposed. The new spatial masking is built according to the image features such as the brightness, edges, and region activities. With the same watermark embedding energy, the quality of watermarked image using the proposed adaptive masking is much better than the one without using the adaptive masking. The wPSNR is used to evaluate the image quality difference which is fed into the new spatial masking function to control the watermark embedding adaptively. The watermark is detected by a key-dependent method without knowing any information of the original image. In addition, we also extend this proposed spatial masking to the DCT domain by searching the extreme value of the quadratic function subject to the bounds on the variables. In experiments, this scheme shows good performance.