DESCRIPTION
i.ifft is an image processing program based on the algorithm given
by Frigo et al. (1998), that converts real and imaginary frequency space
images (produced by
i.fft) into a normal image.
NOTES
The current mask is respected when reading the real and imaginary 
component files;  thus, creating a mask is a primary step for selecting 
the portion of the frequency space data to be included in the inverse 
transform.  The module wxGUI vector digitizer
can be used to create masks while viewing the real 
or imaginary component image. Alternatively r.circle can be 
used to generate high-, low- and donut filters specifying the DC point 
as circle/ring center. When i.ifft is executed, it 
(automatically) uses the same GRASS region definition setting that was 
used during the original transformation done with
i.fft.
SEE ALSO
i.cca,
g.gui.iclass,
i.fft,
i.pca,
r.circle,
wxGUI vector digitizer
REFERENCES
-  M. Frigo and S. G. Johnson (1998): "FFTW: An Adaptive Software 
Architecture for the FFT". See www.fftw.org:
FFTW is a C subroutine library for computing the Discrete Fourier 
Transform (DFT) in one or more dimensions, of both real and complex 
data, and of arbitrary input size.
-  Richards, J.A (1986): Remote Sensing Digital Image 
Analysis, Springer-Verlag, 1986.
-  Personal communication, between program author and Ali R. Vali, 
Space Research Center, University of Texas, Austin, 1990.
AUTHORS
David Satnik, GIS Laboratory, 
Central Washington University
Glynn Clements (FFTW support)
Last changed: $Date: 2014-11-01 11:11:04 +0100 (Sat, 01 Nov 2014) $