面向医学图像的半脆弱水印算法

Semi-fragile Digital Watermarking Algorithm for Medical Image

针对现有认证水印算法篡改定位准确性和安全性不足的问题,该文提出了一种面向医学图像的半脆弱水印算法。首先对医学图像进行分块,计算图像块中高5位比特的灰度均值作为水印信息,将其嵌入图的2个最低有效位中;然后按照奇偶法重新计算水印作为认证水印,将其嵌入图的最低第3有效位中;最后比较认证水印和提取水印之间的相似度,当水印的相似度高于0.6时,认证定位结果正确,否则,认证该结果是错误的,应该舍弃。实验结果表明,该算法大大降低了篡改定位结果的虚警概率,并且篡改定位精度、准确性和安全性都比较高。

Concerning of the issue that the present authentication algorithm＆#39;s positioning is on a low accuracy and security condition , a semi-fragile watermark algorithm for medical image has been put forward in this paper.Firstly, an original image is separated into blocks , then to calculate the high 5-bit gray-scale for the mean of each pixel as the image characteristics watermark information , and embed it in the two least significant bit of the host image.According to the method of parity to recalculate the watermark as authentication watermark , and embed it in the third from bottom in the significant bit .Finally compare the similarity between the authentication watermark and the extracted watermark .When the similarity is higher than 0.6, the certification is correct , otherwise , it is wrong .The experimental results show that the algorithm of false-alarm probability is 0 , and it has a high precision , accuracy and safety .