I. Introduction
With the rapid development of Internet and the wide application of multimedia technology, people can communicate the digital multimedia information with others conveniently in the internet. In many cases, we hope our image data which are transmitted on the network do not be browsed or processed by illegal receivers. Therefore, the security of digital images attracts much attention recently, and many different methods for image encryption have been proposed. Such as the method for image encryption with fractional Fourier transform (FrFT) [1], and the technique for image encryption using fractional Fourier transform and radial Hilbert transform (RHT) [2]. Another method for optical image encryption using fractional Fourier transform and chaos was proposed by Narendra Singh [3]. Zhao et al proposed an optical image encryption method using fractional Hartley transform [4]. Wu et al proposed a method for image encryption with discrete fractional cosine transform (DFrCT) [5].