实现了Fir汉宁窗设计II型数字低通滤波器，文件中含有子函数文件，运行成功，无错误-The Fir Hanning window design II digital low-pass filter, the file contains sub function files, run successfully, no error

用于进行swi处理，二维hanning窗滤波，最小密度投影(swi processing, 2d-hanning window filter, minimum intensity projection)