频域低通滤波（理想低通滤波器、梯形低通滤波器、巴特沃斯低通滤波器、指数低通滤波器），频域高通滤波（理想高通滤波器、梯形高通滤波器、巴特沃斯高通滤波器、指数高通滤波器）-Frequency-domain low-pass filter (ideal low-pass filter, ladder low-pass filter, Butterworth low-pass filter, the index low-pass filter), frequency-domain high-pass f