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)
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