i.ifft(1grass) GRASS GIS User's Manual i.ifft(1grass)
NAME
i.ifft - Inverse Fast Fourier Transform (IFFT) for image processing.
KEYWORDS
imagery, transformation, Fast Fourier Transform
SYNOPSIS
i.ifft
i.ifft --help
i.ifft real=name imaginary=name output=name [--overwrite] [--help]
[--verbose] [--quiet] [--ui]
Flags:
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
real=name [required]
Name of input raster map (image fft, real part)
imaginary=name [required]
Name of input raster map (image fft, imaginary part
output=name [required]
Name for output raster map
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 com-
ponent 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. Alterna-
tively 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 sub-
routine 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)
SOURCE CODE
Available at: i.ifft source code (history)
Accessed: unknown
Main index | Imagery index | Topics index | Keywords index | Graphical
index | Full index
© 2003-2022 GRASS Development Team, GRASS GIS 7.8.7 Reference Manual
GRASS 7.8.7 i.ifft(1grass)
Generated by dwww version 1.14 on Wed Dec 25 03:00:38 CET 2024.