中文说明：二维通用傅里叶变换
English Description：
2 Dimensional generic Fourier Transform % % [ima_out] = fft2(ima_in,direction) % % This function calculates the complex Fourier transform % of the input image ima_in. If direction is set to 1, the direct fft % is performed, otherwise, the inverse one performed. % % ima_in : input image. Can be real or imaginary % direction: optional parameter. By default, direct Fourier transform is assumed % imafft : output image %