Discrete Cosine Transform Based Watermarking Scheme and Band Selection

Compared with spatial domain based watermarking techniques, transform domain based watermarking techniques have become the main stream of this research area for a long time, since transform domain based watermarking schemes can provide not only good watermarked image quality, but also stronger robustness under general attacks or noise affection. In this chapter, our focus is shifting to the transform domain based watermarking scheme, where a watermarking scheme based on the most popular discrete cosine transform (DCT) is presented. The DCT-based scheme first transforms the cover image into frequency domain. It then selects a number of DCT bands according to the user-specified key and modifies these bands to carry the watermark bits. To have better coding results, the concept of introducing intelligent techniques into the watermarking scheme is employed again. Here a training procedure named genetic band selection (GBS) is illustrated. It employs the genetic algorithm (GA) to select a group of suitable DCT bands for watermarking. The trained result is then used in the mentioned DCT-based watermarking scheme. With the trained result of the GBS procedure, we expect the original watermarking scheme could have better performance.