A Digital Image Watermark Algorithm Taking Use of the Orthogonal Code Spread Spectrum Technology
Rong Tai-ping · Yingxiang jishu · 2005
A digital image watermark algorithm, which takes use of the orthogonal code spread spectrum technology is proposed. First of all, the watermark is modulated by two orthogonal Walsh codes respectively. Then add these two sequences to obtain one to be embedded. Finally, this spread sequence is embedded into the medium frequency and low frequency coefficients of DCT of the original image. At the receiver, the spread signal is extracted first, then demodulated in the correlation detector respectively by the two orthogonal codes, thus two sequences can be obtained. At last, combining them to obtain the final withdrawn watermark. Experimental results show that, the proposed method is of very good performance under noise, cropping and JPEG attacks. Furthermore, it is robust to median filtering.