HVS Based Adaptive Digital Image Watermarking

It is known that there is a trade off between the imperceptibility and robustness of a watermark. 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 watermarking energy, the quality of watermarked image using adaptive masking is much better than the one without using adaptive masking. We analyze that the PSNR cannot distinguish the qualities of two images with the same watermarking energy. We propose to use the wPSNR to evaluate the image quality. The watermark is detected by the 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