I. Introduction
In recent years, Generative Adversarial Networks (GANs) [1] have been studied widely and applied to many fields successfully, such as, text to image generation [2], human faces generation [3], and image to image translation [4], which is an implicit generative model. The GAN consists of a generator network and a discriminator network. The generator network fits the true distribution so as to generate fake data that can deceive the discriminator network. The discriminator network determines whether the input data samples from the true distribution or the generator distribution. GANs find Nash equilibrium when the generator network completely captures the distribution of real data and the discriminator network cannot discern the source of the input data.