OpenCV轮廓一维离散傅里叶变换

Question

A problem happened about Fourier descriptor： if a contour has K point，then let

s（k）= x（k）＋i y（k），k = 0,1，...,K-1.

the s(k) discrete Fourier transform is

a(u)=∑s（k）*e^(-i2πuk/K), k = 0,1，...,K-1.

I want to inverse the contour with a(p) ,p=0,1...,P，the P is less than K. But when use dft function in Opencv:

dft(inputarray,outputarray,DFT_INVERSE,0);

the output array has the same size with input array, how can I get a K points contour with P parameters a(p)? Thanks!!

Answer 1

实际上输出数组的大小应该等于输入数组的大小，修改DFT的数学模型https://ccrma.stanford.edu/~jos/mdft/Mathematics_DFT.html