Forward FFT

Use the FFT2IN GX to apply a Fast-Fourier Transform to an image.

FFT2IN dialog options

Name of input pre-processed grid file

Specify the name of the Input Pre-processed Grid File

Script Parameter: FFT2.IN

Application Notes

A transform grid will be created using the root name of the input grid with extension (*.TRN). By default, this TRN grid will be created in the current working directory. This location can be changed in a script by setting the parameter:

FFT2IN.TRN="full path to grid file.ext(qual)"

A transform grid is a floating-point grid (4-byte reals), in which each pair of points represents the real and imaginary components of a Fourier Transform point. The data storage in transform file is as follows:

NX = original X dimension

NY = original Y dimension

DX = X element separation

DY = Y element separation

WX = 1/(NX*DX), wavenumber increment in X

WY = 1/(NY*DY), wavenumber increment in Y

QX = 1/(2*DX) , Nyquist in X

QY = 1/(2*DY) , Nyquist in Y

0 +WX +QX

r i r i r i

v NY-1 . . . . . . . . . . -WY

e . . . . . . . . . . -WY*2

c . . . . . . . . . .

t . . . . . . . . . .

o . . . . . . . . . .

r . . . . . . . . . .

. . . . . . . . . . -(QY-WY)

^ . . . . . . . . . . QY

| . . . . . . . . . . QY-WY

. . . . . . . . . .

2 . . . . . . . . . . WY*2

1 . . . . . . . . . . WY

0 . . . . . . . . . . 0

0 1 2 (NX+1) -> element

(The X(-)Y(+) portion will be complex conjugate of the X(+)Y(-) portion)

(The X(-)Y(-) portion will be complex conjugate of the X(+)Y(+) portion)