在图像内容认证的数字水印问题的研究中,常规水印算法不能同时在空域和频域检测图像的变化,不能同时对图像的篡改位置和篡改度进行分析与检测,导致图像细节敏感度不足,防篡改敏感度低.因此提出一种基于离散小波域的脆弱水印算法,将脆弱水印同时嵌入到离散小波系数的低频和高频子带中,从而可以获得水印在宿主图像中的空间信息和水印信号的频率扩展信息.利用嵌入水印与提取水印间差异的阈值判定,可以鉴别宿主图像是否被篡改.仿真证明,算法可以检测不同分辨率下的水印篡改图像,并能够实现对篡改的定位,提高检测效果.%The digital watermark for image content authentication is studied. Because of the deficiency that the traditional watermarking algorithm has no way to check the changes of imags concurrently in spatial and frequency domain so that the position and degree can not be analyzed and detected at the same time, a fragile watermarking algorithm based on discrete wavelet domain is proposed which improves the methods for embedding and detecting watermark that fragile watermark is embedded into low and high frequency subbands of wavelet coefficient at same time in order to obtain watermarking spatial information and frequency expansive information in host image. This algorithm has the character of highly sensitive to checking tamper resistance, which can detect forged watermarking images in different image resolution, and implement data tamper locating.
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