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FFT2D

Section: C Library Functions (3)
Updated: 16 Mar 1998
Index

NAME

fft2d, fft - Two dimensional Fourier Transform

SYNTAX

#include <xite/fft.h>

int fft2d( IBAND in_band, IBAND out_band,
int inverse, double scale );

DESCRIPTION

Discrete Fourier Transform.

If inverse= FALSE (0), a forward transform isperformed, otherwise an inverse transform is performed.

scaleis used to scale the output image. Set scaleto 1.0if you don't want scaling. Set scaleto0.0if you want standard scaling (1/(xsize*ysize) inforward transform and no scaling in inverse transform).

The forward and inverse discrete Fourier transformswith standard scaling are given respectively as:

           1    M   N          -j*2*pi*(ux/M + vy/N)
F(u,v) = ---  Sum Sum f(x,y) e
          M*N  x=0 y=0

M N j*2*pi*(ux/M + vy/N)
f(x,y) = Sum Sum F(u,v) e
u=0 v=0

where M=Ixsize(f), N=Iysize(f).

RESTRICTIONS

in_bandand out_bandmust be of the same size and typeIcomplex_typ. Horizontal and vertical band size must bepowers of two.

RETURN VALUE

0 - ok
1 - Bad pixel type
2 - Bad size

AUTHOR

Otto Milvang

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