一种隐藏机密图像的新方法

提出了应用灰度变换差分替代方式进行图像隐藏的方法。该方法首先对机密图像和掩护图像进行灰度变换，然后利用变换后机密图像的象素灰度差值替代变换后掩护图像中相应的灰度差值，生成与掩护图像相似的用于隐藏机密图像数据的伪装图像。该方法生成的伪装图像具有较好的隐蔽性，有效地减小了传统方法生成的伪装图像与掩护图像的视觉差异。同时从伪装图像中恢复的机密图像保真度较高。仿真结果表明，该方法有效可行，在保证机密图像数据完整的前提下生成了比较逼真的伪装图像，伪装图像和恢复的机密图像均具有较高的峰值信噪比。

A New Method for Hiding Secret Image

There exist two shortcomings in the method of gray difference replacement for hiding secret image: (1) the visual effect of the dazzle image is not perfect; (2) some information of the secret image may be lost. We present a new method, which combines the method of gray transform and gray difference replacement to hide secret image. First, secret image and cover image are respectively transformed via gray transform to avoid data overflow caused by following difference operators, and then the gray difference value of the transformed cover image is replaced by that of the transformed secret image and produces a dazzle image similar to the cover image. Since the gray distribution of the transformed secret image is much similar to that of the cover image after difference, the number of cover image pixels whose gray value needs to be adjusted during the course of replacement is reduced, thereby the visual effect of the produced dazzle image is vivid, and the secret image resumed from the dazzle image has higher fidelity. Simulations as given in Fig.3 show that this method not only effectively improves the visual effect of the dazzle image but also reduces the distortion of the secret image; both the dazzle image and the resumed secret image have higher PSNR (Peak Signal to Noise Ratio).