Image Watermarking Algorithms Based on the Discrete Wavelet Transform

Abstract

In the last decade, many digital image watermarking algorithms have been proposed and implemented; however, algorithms based on the discrete wavelet transform (DWT) have been widely recognized to be more prevalent than the others. This is due to the wavelets’ excellent spatial localization, frequency spread, and multiresolution characteristics, which are similar to the theoretical models of the human visual system. In this chapter, we describe three DWT-based digital image watermarking algorithms. The first algorithm watermarks a given image in the DWT domain, while the second and third algorithms improve the basic algorithm by combining DWT with two powerful transforms. The second algorithm is a hybrid algorithm in which DWT and the discrete cosine transform (DCT) are combined. The third algorithm is also a hybrid algorithm in which DWT and the singular value decomposition transform (SVD) are combined. Performance evaluation results show that combining DWT with DCT or SVD improved the imperceptibility and robustness performance of the basic DWT-based digital watermarking algorithm. Finally, the ideas described in the chapter can be easily extended to watermarking multimedia objects that include audio and video data contents.