ROBUST DWT-SVD DOMAIN IMAGE WATERMARKING: EMBEDDING DATA IN ALL FREQUENCIES
Watermarking (data hiding) is the process of embedding data into a multimedia element such as image, audio or video. This embedded data can later be extracted from, or detected in, the multimedia for security purposes. A watermarking algorithm consists of the watermark structure, an embedding algorithm, and an extraction, or detection, algorithm. Watermarks can be embedded in the pixel domain or a transform domain. In multimedia applications, embedded watermarks should be invisible, robust, and have a high capacity .Robustness is the resistance of an embedded watermark against intentional attacks, and normal A/V processes such as noise, filtering ( blurring , sharpening, etc. ) , re sampling, scaling, rotation, cropping, and lossy compression. Capacity is the amount of data that can be represented by an embedded watermark. The approaches used in watermarking still images include least-significant bit encoding, basic M-sequence, transform techniques, and image-adaptive techniques. An important criterion for classifying watermarking schemes is the type of information needed by the detector:Â¢ Non-blind schemes: Both the original image and the secret key(s) for watermark embedding.Â¢ Semi-blind schemes: The secret key(s) and the watermark bit sequence.Â¢ Blind schemes: Only the secret key(s).Typical uses of watermarks include copyright protection, the cost of a watermarking system will depend on the intended use, and may vary considerably . Two widely used image compression standards are JPEG and JPEG2000. The former is based on the Discrete Cosine Transform (DCT), and the latter the Discrete Wavelet Transform (DWT)..