A Reversible Watermark With a New Overflow Solution

Overflow problem is essential to reversible watermarking algorithms, as it would lead to great distortion or irreversibility if not properly handled. In general, the existing algorithms handle overflow problem with methods that take a lot changes to pixels, which consequently brings a possibly poor quality or a high complexity. In order to solve the overflow problem specifically with a higher quality and a lower complexity, and improve the security of watermark, we put forward a new reversible watermarking scheme. We take the strategy of twice embedding—first, the proposed scheme uses wavelet histogram shifting to embed the watermark information; second, a proposed low-distortion overflow processing algorithm (LDOPA) is implemented to process the overflow problem occurred during the first step, which iteratively scans the pixels, modifies the overflow pixels one by one, and embeds the modification record with its authentication information on the image. In addition, we apply logistic mapping, torus mapping, and CRC to improve the security of the watermark, allowing users to extract watermark only when they hold the correct password. The experimental results prove that the scheme realizes the complete reversibility of watermark and carrier image. Especially, the proposed LDOPA can be easily combined with the existing watermarking methods to further improve their performance.