Intel IPP functions that compute FFT and DFT can process both real and complex images. Function flavors operating on real data are distinguished by R suffix present in function-specific modifier of their full name, whereas complex flavors' names include C suffix (see Function Naming).

The results of computing the Fourier transform can be normalized by specifying the appropriate value of

flag

argument for context initialization. This parameter sets up a pair of matched normalization factors to be used in forward and inverse transforms as listed in the following table:

In this table,

N

and

M

denote the length of Fourier transform in the x- and y-directions, respectively (or, equivalently, the number of columns and rows in the 2D array being transformed).

For the FFT, these lengths must be integer powers of 2, that is

N=2

orderX

,

M=2

orderY

, where power exponents

are known as order of FFT.

For the DFT,

N

and

M

can take on arbitrary integer non-negative values.