Digital Watermarking is defined as non detectable marking on images, videos, 3D data, audio or text. They can be read by computer assisted methods. Digital Watermarking may contain several different watermarks simultaneously.
Digital Watermarking is used for different purposes. Digital Watermarking helps in the prosecution of copyright infringement. Unlike metadata, Digital Watermarking directly interwoven with the content to be marked, with steganographic methods. In the case of the robust watermark this integration ensures that the elimination of the watermark makes it unusable.
In various research and development projects that focused initially on the area that processes have been developed mainly for commercially relevant content such as audio and video data and 3D models. There are also Digital Watermarking methods such as for marking databases, musical notes, still images and text.
Occasionally, semi-transparent overlays in images or videos, for example, logos or copyright information, mistakenly referred to as digital watermarking. The usage is misleading, as that neither the carrier (image or video) might not necessarily be available in digital form, the Digital Watermarking is read out digitally. A superimposed semitransparent photo lettering is clearly traceable to the origin, without any need of digital technology.
Digital Watermarking has different characteristics; perceptibility denotes the influencing of the quality of the labeled content, robustness, detectability are other points.
The nature of the embedded message is determined by the application. This can be, for example, in the case of the proof of authorship, information regarding the copyright owner. In the general case metadata is embedded; Unique identification number of the contents similar to the ISBN is used in those cases.
Both classes of methods – digital watermarking and digital fingerprinting – belong to the class of passive protection mechanisms. In contrast to active defense mechanisms, such as encryption which is used to prevent unauthorized access to the content.
A special class of Digital Watermarking are reversible Digital Watermarking techniques. Here, the embedded Digital Watermarking can be removed and the original message can be recovered. This brings you the recovery information in addition to the newly introduced. Applications of this reversible Digital Watermarking technique is used in medical image processing.