A robust digital image multi-watermarking scheme in the DWT domain

Digital watermark is an effective way to protect the rightful ownership of multimedia contents. In this paper, a multi-watermarking scheme is proposed, in which three independent binary watermarks are embedded in a grayscale digital image. In order to embed multi-watermarks simultaneously to improve the quality of watermarked image and also robustness of extracted watermarks, the three 2-D watermarks were first recombined into a 3-D watermarking sequence. Then, the approximation sub-image of the original digital image in the Discrete Wavelet Transform (DWT) domain was decomposed into non-overlapping blocks and the blocks with best abundant texture information were selected according to the size of binary watermark. Finally, the multi-watermark embedding was carried out by modifying the fractional part values of these selected block pixels based on the proposed discrete operation rule. A scheme was also developed correspondingly for multi-watermarking extraction from the distorted image. The experimental results show that one of multi-watermarks is robust enough against the common image processing such as noise addition, filtering, and JPEG compression, while the other two watermarks are immune to any image attacks.