基于Zig-Zag扫描的空域图像置乱新算法

传统的图像置乱算法如基于Arnold变换的数字图像置乱、基于Hilbert曲线图像置乱、基于仿射变换等都是将图像中像素的位置重新排列,从而使原始图像变换成一个杂乱无章的新图像。但是,其本身的像素值并未发生改变,所以置乱后图像的灰度直方图都不发生改变,而灰度直方图又是衡量一幅图像的重要特征。对于那些对安全性要求比较高的领域,如军事或牵涉到国家安全的机构,这类置乱方法的安全性可能达不到人们期望的要求。针对以上问题,本文提出了一种基于Zig-Zag扫描的空域图像置乱新算法。该算法首先对原始图像进行Zig-Zag扫描形成一个一维向量,然后对一维向量中每个像素和它前面相邻的像素进行按位异或运算,同时对其异或运算的结果进行像素值的交叉换位,再次改变像素点的灰度值,从而提高图像置乱效果。实验结果表明,该算法与传统的图像置乱算法相比,置乱后的图像不仅直方图发生了显著改变,而且置乱图像的统计特征更像白噪声,更加适用于图像文件的加密传输和秘密图像信息在数字水印技术中的置乱预处理。

A New Image Scrambling Algorithm in the Space Domain Based on Zig-Zag Scanning

The traditional image scrambling algorithm is accomplished by arranging the pixel’s positions in the original image repeatedly such as image scrambling based on the Arnold transformation,and the image scrambling based on the Hilbert curve transformation,and the image scrambling based on affine transformation. Finally,the original image is converted to a new disorder image ,but the value of the original image’s pixels are not changed.Because of the above reasons,the histogram of image scrambling can not be changed.However,the histogram is an important feature to measure gray images.For some professional fields,such as military departments and national security institutes,these methods of image scrambling can not meet our desirable demand. Considering all the above problems,this paper presents a new image scrambling algorithm in the space domain based on Zig-Zag scanning.The algorithm does Zig-Zag scanning for the original image firsts.Meanwhile,the original image can be converted to a 1-D vector.Furthermore,making a bit-exclusive-or operation on each pixel with its prior one first,and then the bits of each pixel value are cross-exchanged;thereby the effect of image scrambling is improved again.The experimental results show that compared with some existing algorithms,the method not only provides a scrambling image whose histogram is changed obviously,but also the scrambled image looks more like the Gaussian noise,which is expected being applied into the image encryption transmission or the preprocessing of secret images in digital watermarking.