High-Capacity Reversible Watermarking Algorithm Research Based On Medical Image

Digital Watermarking is a new type of copyright protection technology. The distinctive feature of reversible watermarking algorithm is that after the extraction of the watermark information the original image can be lossless restored. It is very useful in medical images, remote sense images, and legal images, etc. Those kinds of images request high image quality, so after extracted the watermark information the image should be perfect recovered. Medical images are different from natured pictures mainly in characteristics such as high image accuracy, relatively smooth and a lot of blank areas (The areas have no information and are black). In this paper, according to the characteristics of medical images, two reversible watermarking algorithms are proposed. Those algorithms can both use for natured pictures and medical images.1. A reversible high-capacity watermarking algorithm for medical images is proposed based on the parity of data. This algorithm completely utilizes all pixels which are able to carry watermark information, so the embedded rate of the image is enhanced. To ensure the correct classification of pixels before extracting and the reversibility of the algorithm, the testing algorithm is improved by using the parity of data. Experiments show that this algorithm can both improve the watermarking capacity and guarantee perceptual quality.2. A reversible watermarking algorithm of encrypted image based on sorting and selection is proposed. At present, watermark information which is embedded in encrypted image is low.Our algorithm can improve the capacity and the visual effects through sorting and selecting the relatively smooth area. This area could be divided into small pieces and embed information. Experiments proved the effectiveness of the algorithm.