用C++实现了MATLAB中fftshift及triang函数功能，代码是实现此二功能的函数

矩形连续函数的傅立叶变换：构建一个矩形函数，对f进行补零，而后进行二维快速傅立叶变换：使变换结果的零频率分量位于中心，调用函数fftshift：映射和重建图像-Fourier transform of rectangular continuous function: for a rectangular function, the zeros of f, then the two-dimensional fast Fourier transform: the transform results o

理想低通滤波器，巴特沃斯低通滤波器，高斯低通滤波器，使用FT和IFT，说明fftshift的作用。-Ideal low-pass filter, Butterworth low-pass filter, Gaussian low-pass filter, the use of FT and IFT, descr iption fftshift role.

SAR RD 成像算法，ftx与fty分别为方位向和距离向fft，需要对fft进行两次fftshift-SAR RDimaging algorithm

绘制一幅人像或风景图像的幅频图及相频图,并由幅频图及相频图重建空间域图像.(使用fft2,ifft2,fftshift函数)-Draw a portrait or landscape image amplitude-frequency and phase-frequency diagram in Figure by the amplitude-frequency and phase-frequency diagram in Figure spatial domain image reconstr