Abstract: The new image scrambling effect evaluation method based on mutual information distance of difference image was proposed. The new concept of mutual information distance based on mutual information was firstly proposed, and then the difference image of the original image and scrambled image was obtained by means of difference operation on two images. At last the mutual information of two difference images was computed and acted as the new criteria of image scrambling effect evaluation. Experimental results show that the proposed method is effective to describe the relation between the scrambling effect and the number of iterations in the scrambling techniques, which is largely consistent with human vision. For different images, when some transformation is used, this evaluation method can reflect to some extent the scrambling effects in each scrambling stage.

Key words: mutual information distance

摘要： 提出了差分图像和互信息距离相结合的图像置乱效果评价新方法。首先提出了互信息距离概念，然后对置乱前后图像进行差分运算并得到其相应的差分图像，最后计算两差分图像之间的互信息距离作为图像置乱效果评价的新准则。实验结果表明，所提出的评价方法能够较好地刻画图像的置乱程度，反映了加密次数与置乱程度之间的关系，与人的视觉基本相符。而且对于不同的图像，该评价方法能在一定程度上反映所用的置乱变换在各置乱阶段的效果。

关键词: 图像置乱, 置乱度, 差分图像, 互信息距离, image scrambling, scrambling degree, difference image