Medical image watermarking for copyright protection based on Visual Cryptography

Image watermarking is one of multiple techniques that protect digital image against malicious attacks by embedding a signature into the cover image. But despites its attractiveness, watermarking methods may encounter limitations in medical images. The added watermark signal frequently alters the host medical image in an irreversible manner and may mask subtle details. Consequently, we propose a method for medical image copyright protection that may remedy this problem. The proposed method is a robust image watermarking scheme based on Dual Tree Complex Wavelet Transform (DT-CWT) and Visual Cryptography concept (VC). This method does not require that the watermark to be embedded into the original image which leaves the marked image equal to the original one. In the concealing and extracting process, secret and public shares are generated respectively; those two shares are stacked together to extract the watermark from the attacked image. To improve the visual quality of the extracted watermark, a post process called reduction procedure is also proposed. The experimental results show that the proposed method can withstand several image processing attacks such as cropping, filtering and compression etc.