f(i,j)=∑z,wg(z,w)h(i−z,j−w)f(i,j)=\sum\limits_{z,w}g(z,w)h(i-z,j-w)f(i,j)=z,w∑g(z,w)h(i−z,j−w),这个怎么用FFT维护亚
