本程序主要实现了离散时间的傅立叶变换，具有很强的可移值性，原理简单。-This procedure has been the main achievement of the discrete-time Fourier transform, has a strong value can be changed, and simple.

读入.pgm格式的灰度图文件，进行二维离散傅里叶变换并且显示-Read. Pgm format, grayscale documents, conducting two-dimensional discrete Fourier transform and show