结合二次差值扩展与插值扩展的可逆图像水印算法

Reversible image watermarking algorithm combining quadratic difference expansion with interpolation expansion

为了提高现有可逆图像水印算法的视觉质量和嵌入率,提出了一种结合二次差值扩展和插值扩展的可逆图像水印算法。首先去除原始图像中的0和255像素点;然后对去除0和255像素点后构成的新图像进行互不重叠块划分并对划分出的每个图像块进行插值扩展;接着将前一半置乱后的水印信息利用一次差值扩展嵌入到经插值扩展生成的图像块中;最后利用二次差值扩展将剩余的一半水印信息嵌入到之前生成的水印图像中,去除扩展的像素点和并上之前已去除的0和255像素点,以此生成最终的水印图像。实验结果表明该算法不仅嵌入率高,而且有较高的视觉质量(平均PSNR值高达77.91dB),能实现原始图像的完全恢复。和其它基于差值扩展的可逆图像水印算法相比具有一定的优势,无需考虑嵌入区域的平滑度。

To improve the visual quality and embedding rate of the existing reversible image watermarking algorithm,a reversible image watermarking algorithm combining quadratic difference expansion and interpolation expansion is proposed.Firstly,the pixel points with grayscale values 0 and 255 in the original image are removed;then,the new image composed after removing the pixel points with grayscale values 0 and 255 are divided into non overlapping blocks and each block is interpolated;the first half of scrambled watermark information is embedded in the image block generated by the interpolation expansion using the primary difference expansion;finally,the remaining half of the watermark information is embedded into the previously generated watermarked image using the secondary difference expansion.Removing the extended pixel points and the pixel points with grayscale values 0 and 255 which have been removed before to generate the final watermarked image.The experimental results show that the algorithm both has a high embedding rate and a high visual quality(the average PSNRvalue is as high as 77.91 dB),which can completely recover the original image.Compared with other reversible image watermarking algorithms based on difference expansion,this algorithm has certain advantages without having to consider the smoothness of the embedded image region.