Difference between revisions of "fftn(API)"

Latest revision as of 04:12, 6 August 2014

DataManip/mrcImage/src/fftn is API for FFT.

constant

struct

API

Release memory

Release the used memory in fftn.c for FFT.

extern void fft_free (void);

FFT

double

extern int fftn (int ndim, const int dims[], double Re[], double Im[],
		 int isign, double scaling);

float

extern int fftnf (int ndim, const int dims[], float Re[], float Im[],
		  int isign, double scaling);

Re, Im: Input-Output

Variables mean

Variables in These API are used as the following.

Re[]:		real value array
Im[]:		imaginary value array
nTotal:	total number of complex values
nPass:	number of elements involved in this pass of transform
nSpan:	nspan/nPass = number of bytes to increment pointer
		in Re[] and Im[]
isign:	exponent: +1 = forward  -1 = reverse
scaling:	normalizing constant by which the final result is *divided*
	scaling == -1, normalize by total dimension of the transform
	scaling <  -1, normalize by the square-root of the total dimension