基于仿射变换的图像置乱改进新算法

传统的仿射变换的图像置乱算法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我们期望的要求。针对以上问题,该文提出了一种基于仿射变换的图像置乱改进新算法。该算法首先对原始图像进行仿射变换,然后对变换后的图像进行Zig-Zag扫描形成一个一维向量,再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和安全性。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 Improved Image Scrambling Algorithm Based on Affine Transform

Traditional image scrambling algorithm based on affine transform is accomplished by arranging the pixels position in original image repeatedly.Finally,the original image is converted to a new disorder image,but the value of original image pixels are not changed.Because above reasons,the histogram of image scrambling can＇t be changed,however,the histogram is an important feature to measure a gray image.For some professional fields,such as： military department,or national security institutes.So those methods of image scrambling can not arrive at our desirable demand.Considering all above problems,this paper presents a new improved image scrambling algorithm based on affine transform.Firstly the algorithm does affine transform for original image,then Zig-Zag scan can be used,so the original image can be converted to one-dimensional vector,furthermore,making a bit-exclusive-or operation on each pixel with prior one first,and the bits of each pixel value are exchanged across;thereby the effect and security of image scrambling is improved again.The experimental results show that compared with some existing algorithms,the method not only provides with a scrambling image whose histogram has been changed obviously,but also the scrambled image look more like Gaussian noise,which is expexted when being applied into the image encryption transmission or the preprocessing of secret images in digital watermarking.