 
Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
 Updated manual page: here
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.
i.cca,
g.gui.iclass,
i.fft,
i.pca,
r.circle,
wxGUI vector digitizer
-  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.
David Satnik, GIS Laboratory, 
Central Washington University
Glynn Clements (FFTW support)
Last changed: $Date: 2014-11-01 03:07:51 -0700 (Sat, 01 Nov 2014) $
SOURCE CODE
Available at: i.ifft source code (history)
Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
 Updated manual page: here
Main index |
Imagery index |
Topics index |
Keywords index |
Graphical index |
Full index
© 2003-2019
GRASS Development Team,
GRASS GIS 7.2.4svn Reference Manual