基于混合整数变换的高容量可逆数字水印

High-Capacity Reversible Watermarking Based on Mixed Integer Transform

提出了一种基于混合整数变换的高容量可逆数字水印算法。该算法首先将图像分割成3×3的小块,从第一个图像块开始进行9像素的整数变换。然后应用压扩算法减小差值,并采用扩差法嵌入水印。引入压扩算法极大地增加了可扩的图像块的数目。对于不可扩的3×3像素块,算法进一步将其分割为3×1的图像块,应用3像素的整数变换,同样采用压扩算法和扩差法嵌入水印。混合嵌入方案和压扩算法的引入能够获得更易压缩的位置图,从而最大限度地提高了水印的容量。该算法一次嵌入的极限容量为8/9 bpp(比特/像素)。实验结果表明,本算法的透明性好,容量高。

A novel reversible data hiding scheme based on mixed integer transform is presented. On a grayscale image, every 3 × 3 adjacent pixels are grouped into an ennead. A nine-pixel block integer transform is applied to each ennead to obtain its transformed one. After that, the companding technique is used to compress its eight difference values. Then, data embedding is carried out by expanding smaller differences. The introduction of the companding technique increases the number of ennead available for embedding. For the non-expanded ennead, a threepixel block integer transform is introduced so as to embed two bits into the triplet. Because the location map for recording these expanded positions can be efficiently compressed for the mixed integer transform, a high hiding capacity is achieved. The method can achieve embedding rate of close to 8/9 bpp at once embedding. Experimental results show that the method is effective on the transparency and the capacity.