Robust Watermark Based On Wavelet Transform

In this paper we systematically expound the concept of digital watermarking technology, the basic principles and other relevant characteristics .Then we study the theoretical model of digital watermarking, and introduce the common watermark attacks. At the same time on the basic principles of wavelet transform, we study the basic processing of the wavelet-domain watermarking algorithm. In accordance with human visual system (HVS), this paper adopts a new digital watermarking technique which is based on discrete wavelet transform (DWT).First of all, the watermark image scrambling approach called Arnold is used where the number of scrambling is used as the key of the digital watermarking system, which is used to increasing the security of watermarking system. Then we make scrambling images and the original image do discrete Haar wavelet transform with one or three levels respectively. In order to select the right location for embedding the watermarking image, we make the wavelet-transformed image analysis at each level. The watermark information at each level is repeatedly embedded into the wavelet-transformed image on each floor. We extract the watermark at each level and the results have high accuracy.The method we adopt in this paper makes full use of multi-resolution wavelet analysis features. Experimental results show that the algorithm improves the capacity of the watermark to some extent, the images which are processed by the algorithm have strong robustness when attacked by cropping, JPEG compression and so on.