基于分块预测的差值直方图平移的可逆水印算法

Reversible watermarking algorithm for difference histogram shifting based on segmenting block prediction

提出一种基于分块的预测差值直方图平移的可逆水印算法。在保持图像视觉效果的前提下,简化了算法步骤,嵌入和提取水印前,不需要进行复杂的预处理,只需要进行分块即可。算法首先把图像划分成4×4的图像块,然后每4个像素为一组,选取1个像素和它周边的3个像素,使用周边3个像素生成预测值,使用预测值与选取的像素进行比较,产生差值,差值进行向下取整,一个图像块内生成4个差值。然后生成差值直方图,选取0值点作为判断标准,差值为0可以嵌入水印。实验表明,该算法不仅可以实现可逆水印,而且水印不可见性较好,实验简单易行,嵌入水印后图像的PSNR高,图像视觉效果好。

In this paper a reversible watermarking algorithm for difference histogram shifting based on segmenting block prediction was proposed.The algorithmic steps were simplified by maintaining the visual effects of the image with minimum complicated preprocessing,but requires a block before embedding and extracting the watermark.Initially,the image was divided into 4*4 image blocks and one group was set up for every four pixels.For each group,one pixel and its three surrounding pixels were selected.The surrounding three pixels were used to generate prediction values,which were then compared with the selected pixels to generate difference.The difference was rounded down and thus four differences were generated in one image block.Then,the difference histogram was generated,in which the difference was basically concentrated near zero value point because it was the difference between the predicted value of surrounding pixels and the selected pixel.The zero value point was selected as the judgment standard and watermarking could be embedded when the difference value was zero.Experiments show that the proposed algorithm can achieve reversible watermarking with better invisibility.Despite the simple and easy operation of the method proposed,the visual effect of the image after watermarking is embedded is of effective quality with higher PSNR.