Abstract: A new image scrambling effect evaluation method based on singular value decomposition of difference image is proposed.Considering the shortcoming of singular value decomposition based image scrambling degree evaluation method not being capable of reflecting that image scrambling effect is good or bad，this paper first obtains the one and two order difference images of the original image and scrambled image by means of difference operation on two images，then the two kinds of difference images are decomposed by singular value decomposition，lastly the discrepancy degree of Singular values of difference images is 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 largely consists 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: image scrambling, scrambling degree, difference image, singular value decomposition

摘要： 提出了基于差分图像和奇异值分解相结合的图像置乱效果评价新方法。针对基于奇异值分解法的置乱程度评价法不能客观地反映图像置乱效果好坏的不足，首先对置乱前后图像进行差分运算并得到其相应的差分图像，其次对两差分图像进行奇异值分解，最后计算其奇异值差异程度的大小作为图像置乱效果评价的新准则。实验结果表明，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。对于不同的图像，该评价方法在一定程度上反映了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, 奇异值分解