Using key points to improve robust reference watermarking algorithm

Robust reference watermarking (RRW) is a digital watermarking algorithm of still images based on the concept of multiresolution wavelet fusion. The aspects of the human visual system are integrated into watermarking algorithm and the concept of "key points" is applied to watermarking in order to improve the robustness of RRW. Normal RRW use only a const Q to quantize wavelet coefficient. In the quantization, process of improved method, if the watermark point is key point, then use larger quantizing parameter Q to quantize wavelet coefficient, or else use smaller Q. When detecting watermark, key points' weight value are 1, and others' are a const that is not smaller than 0 and not larger than 1. Analysis is provided to compute the probability of false positive and false negative results. Experimental results show the performance of our method is better than the original RRW method and demonstrate its potential for the robust watermarking of photographic imagery.