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
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.
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.
- 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.
i.cca,
g.gui.iclass,
i.fft,
i.pca,
r.circle,
wxGUI vector digitizer
David Satnik, GIS Laboratory,
Central Washington University
Glynn Clements (FFTW support)
SOURCE CODE
Available at:
i.ifft source code
(history)
Latest change: Friday Oct 25 16:16:09 2024 in commit: 4ea983fff87951516b6e4578a0527e3b10f04643
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GRASS Development Team,
GRASS GIS 8.4.1dev Reference Manual