i.ifft1grass
Inverse fast fourier transform (ifft) for image processing.
Usage
i.ifft
i.ifft --help
i.ifft real=name
imaginary=name
output=name
[--overwrite]
[--help]
[--verbose]
[--quiet]
[--ui]
Keywords
imagery, transformation, Fast Fourier Transform
Overview
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.
References
- •
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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.
- •
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Richards, J.A (1986): Remote Sensing Digital Image
Analysis, Springer-Verlag, 1986.
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Personal communication, between program author and Ali R. Vali, Space Research Center, University of Texas, Austin, 1990.
Source code
Available at: i.ifft source code (history)
Accessed: Monday Feb 24 17:51:40 2025
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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual
Releases
10 releases since Debian 4.0 (Etch); the text changed 9 times.