Fourier Transforms

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.

• Real - Complex Packed (RCPack2D) Format
  
• FFTInitAlloc
  Allocates memory and fills in context data needed for the image FFT functions to operate.
• FFTFree
  Deallocates memory used by the FFT context structure.
• FFTGetBufSize
  Determines the size of external work buffer that can be used by the FFT functions.
• FFTFwd
  Applies forward Fast Fourier Transform to an image.
• FFTInv
  Applies an inverse FFT to complex source data and stores results in a destination image.
• DFTInitAlloc
  Allocates memory and fills in context data needed for the image DFT functions to operate.
• DFTFree
  Deallocates memory used by the DFT context structure.
• DFTGetBufSize
  Determines the size of work buffer that can be used by the DFT functions.
• DFTFwd
  Applies forward discrete Fourier transform to an image.
• DFTInv
  Applies an inverse DFT to complex source data and stores results in a destination image.
• MulPack
  Multiplies two source images in packed format.
• MulPackConj
  Multiplies a source image by the complex conjugate image with data in packed format and stores the result in the destination buffer in the packed format.
• Magnitude
  Computes magnitude of elements of a complex data image.
• MagnitudePack
  Computes magnitude of elements of an image in packed format.
• Phase
  Computes the phase of elements of a complex data image.
• PhasePack
  Computes the phase of elements of an image in packed format.
• PolarToCart
  Converts an image in the polar coordinate form to Cartesian coordinate form.
• PackToCplxExtend
  Converts an image in packed format to a complex data image.
• CplxExtendToPack
  Converts a complex data image to an image in packed format.

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