Robust image watermark with wavelet transform and spread spectrum techniques

In this paper; the wavelet packet transform[1] and spread spectrum techniques are used to achieve the image watermark processing. In the first stage of the proposed method the original image is converted to frequency domain with wavelet packet transform. After that, the watermark is embedded to the image by adding the data into the significant coefficients in the wavelet packet domain. With this scheme, the watermark data won't be easily distorted when some processing such as compression and translation ape performed. In addition, the spread spectrum technique is adopted to increase the security of the watermark. The pseudo-noise sequence is utilized to decide which subband of the wavelet packet transform is performed such that only the authorized people who have the pattern of the pseudo-noise sequence can retrieve the watermark data. From the simulation results, the approach is with good performance and robust to image processing and attack.