Overview of Various Digital Image Watermarking Methods

Digital watermarking is the method which promises to tackle the piracy of multimedia. In digital watermarking, the watermark data (information related to publisher, file transaction/ downloading records, user identity, etc.) is embedded into the original multimedia object, in hidden format without affecting the normal usage of original file. Many algorithms are available for image watermarking based on histogram, spread spectrum, quantization, discrete cosine transform (DCT). From the previous research, it is clear that, there is a trade-off between the imperceptibility, embedding capacity and robustness. Different methods fulfill different extent of these parameters. Most of the methods do not improve the imperceptibility, embedding capacity, security and robustness satisfactorily. In applications such as, covert communication, embedding capacity must be high, while robustness against geometric attacks is not mainly concerned. The watermarking method based on DCT can normally achieve comparatively high embedding capacity than other methods under given imperceptibility and robustness. Hence, to further enhance the embedding capacity we can develop an algorithm based on discrete cosine transform.