Overview

Watermarking based on transform domain is mostly encountered in literature. Transform-domain watermarking schemes, also called multiplicative watermarks, are generally considered to be robust against attacks. In this chapter, we introduced the fundamental methods for embedding and extraction of the watermarks in the transform domain. These schemes can apply directly to discrete cosine transform (DCT)-domain watermarking, and can also apply to other transformations, including discrete Fourier transform (DFT) and discrete wavelet transform (DWT), with some modifications to fit the characteristics of different transforms. The readers are encouraged to refer to the subsequent chapters in this book with the fundamental concepts of transform-domain watermarking to be described in this chapter.

1 Introduction

For image, audio, and video compression algorithms, transform coding is one of the most important building blocks for processing with the input multimedia. Therefore, watermarking based on transform domain is mostly encountered in literature. Among the practical schemes, discrete Fourier transform (DFT) (Oppenheim and Schafer 1999), discrete cosine transform (DCT) (Rao and Yip 1990), and discrete wavelet transform (DWT) (Akansu and Medley 1999, Rao and Bopardikar 1998) are the most popular transform coding schemes for academic researches and practical implementations.

Watermarking related to transform coding schemes are referred to as multiplicative watermarking. Multiplicative watermarks are automatically image content dependent and are automatically embedded mainly into the perceptually most significant components of the image if the robustness requirement is the main concern for protecting the image content (Langelaar et al. 2000). The...