一种空间域自适应低失真防篡改图像数字水印方案

为提高嵌入水印后的图像质量，提出一种空间域自适应低失真防篡改图像数字水印方案。该方案的水印嵌入位置由混沌密钥确定，以使水印能均匀、随机嵌入到图像的各个部位；采用S LSB算法将水印嵌入到图像像素的次低位，使其能够抵抗一些非恶意的图像水印攻击。该嵌入算法下水印图像的峰值信噪比（peak signal to noise ratio, PSNR）由水印长度和混沌位置密钥决定。为提高水印图像的质量，在给定水印的情况下，自适应地调整水印位置密钥，使水印图像的PSNR达到给定的要求；为降低算法的运算量，快速完成混沌位置密钥的自适应调整，进一步提出分段自适应水印算法。实验表明，该算法能够获得满足应用需求的PSNR，且对一些常用篡改操作能给出篡改率和篡改位置。

A Spatial Domain Adaptive Low Distortion Tamper Proof Digital Image Watermarking Scheme

To improve the imperceptibility of watermarked images,a spatial domain adaptive low distortion tamper proof image digital watermarking scheme is proposed.The embedding position of the watermark in this scheme is determined by the chaotic key,so that the watermark can be evenly and randomly embedded in various parts of the image.The S LSB algorithm is used to embed the watermark in the second least significant bits of the image pixels,making it resistant to some non malicious image watermarking attacks.The peak signal to noise ratio (PSNR) of the watermarked image under this embedding algorithm is determined by the length of the watermark and the chaotic location key.Therefore,in order to improve the quality of the watermarked image,in the case of a given watermark,the watermark position key is adaptively adjusted,so that the PSNR of the watermarked image meets the given requirements.In order to reduce the computational complexity of the algorithm and quickly complete the adaptive adjustment of the chaotic location key,a segmented adaptive watermarking algorithm is further proposed.Experiments show that the algorithm can obtain PSNR that meets the requirements for application,and give the tampering rate and tampering location for some common tampering operations