A novel gray scale watermarking algorithm in wavelet domain

This paper presents a robust better gray image watermarking algorithm based on the distance in the wavelet transform domain. Firstly, two images will be pretreated: the vector image is transformed into discrete wavelet domain, the level of transform is decided by the size of the watermark image, another pretreatment is that watermark image is scrambled by Arnold transform; Secondly, the edge information which is a binary image is extracted from horizontal and vertical details, and compute the their distance transform matrix which are gray-scale images. After that, the scrambled watermark will be embedded in distance transform matrix using the rule of addition, what is more, the strength parameter of embedding is adaptive, and compute their complements; Finally, The last step is the reconstruction of the watermarked image using inverse discrete wavelet transform according to secret key. The experimental results show that this algorithm has good anti-offensive and security. it has the characteristics of the frequency and spatial, and changes the attitude that the detail coefficients have poor robustness. Distance transform can expand energy of image, so, if the watermark is embedded here, the robustness and invisibility are gained at the same time.