With the rapid
growth of Internet and networks technique, multimedia data transforming and sharing
is common to many people. Multimedia data is easily copied and modified, so necessity
for copyright protection is increasing. It is the imperceptible marking of multimedia
data to "brand" ownership. Digital watermarking has been proposed as
technique for copyright protection of multimedia data. Digital watermarking invisibly
embeds copyright information into multimedia data. Thus, digital watermarking
has been used for copyright protection, finger printing, copy protection and broadcast
monitoring. Indeed, a watermarking algorithm requires both invisibility and robustness,
which exist in a trade-off relation. Thus good watermarking algorithm must be
satisfied the requirements.
The
process of digital watermarking involves the modification of the original multimedia
data to embed a watermark containing key information such as authentication or
copyright codes. The embedding method must leave the original data perceptually
un-changed, yet should impose modifications which can be detected by using an
appropriate extraction algorithm. Common types of signals to watermark are images,
music clips and digital video. The application of digital watermarking to still
images is concentrated here. The major technical challenge is to design a highly
robust digital watermarking technique, which discourages copyright infringement
by making the process of watermarking removal tedious and costly.