fft2d

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Name

fft2d - Two dimensional Fourier Transform

Syntax

 fft2d [<option>...] <inimage> <outimage>

Description

fft2d performs a 2 dimensional Fourier transform.

If inimage is of another pixeltype than single precision complex, inimage will be converted to single precision complex. When inimage is double precision complex, this is only allowed when using option -r below.

The forward and inverse discrete Fourier transforms with 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

Horizontal and vertical image size must be powers of two.

Options

-i
Inverse Fourier transform.

-s scale, -fftscale scale
The output image is multiplied by scale. Default scale is 1/(xsize*ysize) for forward transform and 1.0 for inverse transform.

-b
Pixeltype for outimage will be unsigned byte, through conversion of the result. Values outside the range of unsigned byte will be limited to the min/max values for unsigned byte.

Default: Complex.

-r
Allow pixeltype of inimage to be double complex. Convert image to pixeltype complex before applying the Fourier transform.

Default: Allow only single-precision complex or non-complex pixeltype for inimage, not double complex. Convert the image to pixeltype complex before applying the Fourier transform.

Return value

 0 - ok
 1 - error

See also

fft2d(3), absValue(1), power(1), phase(1), real(1), imag(1), fftMagPhase(1), multiply(1)

Author

Otto Milvang

Id

$Id: fft2d.c,v 1.34 1997/05/25 11:55:32 svein Exp $