Abstract: In order to objectively and automatically evaluate the degree of digital image scrambling，the paper suggests a subimage-histogram correlation based blind approach.In the method，the definition and the feature of the ideal scrambled image is analyzed first，whose histogram is summarized at the same time.And then，the scrambled image is divided into some subimages to construct some histogram sequences.Subsequently，image scrambling degree is assessed via the correlation of subimage-histograms.Finally，two kinds of experimental results indicate that compared with the method based on SNR，the method not only is efficient，flexible，running without the origin image involved，but also can provide with some conclusions which are consistent with the perception of human visual system.

Key words: image scrambling, scrambling degree, histogram, correlation, Signal-to-Noise Ratio（SNR）

摘要： 为客观、自动地评价图像置乱效果，提出了一种基于子图直方图相关的图像置乱盲评判方法。该方法首先分析理想置乱图像的定义和特征，归纳总结最优置乱图像的直方图特点；然后，将待评判的置乱图像进行分块处理，建立各子图的直方图序列，利用各序列间的相关度给出置乱程度的评判测度。两种不同类型的置乱效果评判实验显示，与基于SNR的置乱评价方法相比，该方法不仅高效、灵活，评判不需要原始图像做参考，而且评判结果与人类视觉系统的主观感知相吻合，可快速有效判断图像置乱程度。

关键词: 图像置乱, 置乱效果, 直方图, 相关度, 信噪比