Image Processing

7Image Watermarking

The word “watermarking” has been in existence for several hundred years (watermarks on the banknotes and letterheads are typical examples). However, the term “digital watermark” appeared only in the late 1980s, while the real researches and applications of watermark on images started from the mid-1990s.

Image watermarking, a kind of image technology, can be divided into image space domain techniques and transform domain techniques, depending on its processing domain. Since many international standards for image coding and representation use discrete cosine transform (DCT) and discrete wavelet transform (DWT), image watermarking tasks are performed in DCT domain and DWT domain.

In general, image watermarking is a way of information ...