  In this paper, after reviewing the main points of image encryption and
threshold function, we introduce the methods of chaotic image encryption based
on pseudorandom bit padding that the bits be generated by the novel generalized
threshold function (segmentation and self-similarity) methods. These methods
decrease periodic effect of the ergodic dynamical systems in randomness of the
chaotic image encryption. The essential idea of this paper is that given
threshold functions of the ergodic dynamical systems. To evaluate the security
of the cipher image of this scheme, the key space analysis, the correlation of
two adjacent pixels and differential attack were performed. This scheme tries
to improve the problem of failure of encryption such as small key space and
level of security.
