what is the time complexity

if i will depend on fft2 for calculating weighted mean and variance of image and i will do that several times with a for loop, what will be the time complexity?? will it be O(kNlog_2(N)) where N is the image size and k is the no of times of for loop ??

Answer 1

[Walter Roberson]

O(k*N^2*log2(N))

for square matrices.

http://fourier.eng.hmc.edu/e101/lectures/Image_Processing/node6.html and look for "Matrix Form of 2D DFT"

[Doaa Adel]

thanks alot