基于混沌映射的图像置乱是图像加密的一种常用方法。为了增加图像置乱网络的复杂度和提高网络运行的速度，提出了一种改进型基于混沌的图像置乱网络。该网络首先对混沌映射区间进行二次划分．然后在二次划分的区间上将混沌映射的迭代值动态量化为置乱图像的坐标，从而不仅克服了有限精度下混沌轨道遍历混沌映射区间的时间复杂度高的问题，而且减少了搜寻新坐标的迭代次数。另外，还通过计算机实验，对置乱网络的遍历时间复杂度及其置乱性质进行了分析。结果表明，这种置乱网络不仅提高了算法的运行速度，而且增加了密钥参数和密钥空间，具有良好的置乱性质，可以有效地保障加密图像的安全性。

The picture scrambling algorithms based on chaos are frequently used for images secure communications. In this paper, a new modified method of chaotic picture scrambling network is proposed by the chaotic mapping interval twice division and the chaotic orbits dynamic quantification. The new scrambling network adds the complexity and speeds up the computation of the network, since it overcomes the disadvantage that it need large number of computation to make the chaotic orbits ergods the whole chaotic mapping interval under the finite computational accuracy, reduces the computation. The paper also analyzed the time complexity and the scrambling performance of the new networks by computer experiments. The results show that this picture scrambling network has good scrambling capability and guarantees the security of the encrypted images effectively because it can work quickly with large cryptographic keys space.