数字图像置乱程度是评价数字图像置乱算法的重要方面，对数字水印算法的研究也起到重要的指导作用。利用灰度级出现频数可以对数字图像的最佳(理想)置乱效果进行描述，以数字图像的最佳(理想)置乱效果为参照系，基于灰度级出现频数提出了一种衡量数字图像置乱程度的新方法。采用Matlab为实验研究工具，进行仿真实验。实验结果表明，该置乱程度衡量方法与视觉的主观评价基本一致，具有对各种类型的图像加密方法都适用的高泛化性，还具有与原图像无关性。

Digital image scrambling degree is one of the most important aspects of evaluating digital image scrambling algorithm，it has significant effects on the research of digital watermark algorithm. It can describe the best effects of digital image scrambling by taking the frequency of gray levels. Using the best effects of digital image scrambling as parameters, this paper has presented a new method of measuring digital image scrambling degree based on the frequency of gray levels. Emulational experiments have been carried out in MATLAB. The results of the experiment have suggested that the digital image scrambling degree evaluation method is the same as all sorts of image encrypting. The resulting digital image scrambling degree is accordant with visual subjective evaluation, it would not differ a lot for the sake of the changing of its former image as well.