Home
About ISIS
Support
Download

ISIS 3

Documentation
Tutorials
Technical Documents

ISIS 2

Documentation
Tutorials
Technical Documents
USGS

ISIS 3 Application Documentation

fft

Standard View | TOC | Home

Apply a Fourier Transform on a cube

Description
Categories
Groups
Examples
History

Description

This programs takes a single input cube, applies a Fourier Transform, and stores the result in two bands of an output cube containing the magnitude and phase angle data. If the original image has dimensions that are not powers of two, it is automatically padded with zeroes. These images can then be used in the ifft program to recover the original.

Categories

Related Objects and Documents

Applications

Parameter Groups

Files

Name Description
FROM Input file to apply the transform to
MAGNITUDE Magnitude output cube
PHASE Phase output cube

Handling Special Pixels

Name Description
REPLACEMENTReplacement value

Files: FROM

Description

The input cube on which the Fourier transform is applied.

Type cube
File Mode input
Filter *.cub

Files: MAGNITUDE

Description

The resultant cube containing the image magnitude data.

Type cube
File Mode output
Pixel Type real
Filter *.cub

Files: PHASE

Description

The resultant cube containing the image phase angle data..

Type cube
File Mode output
Pixel Type real
Filter *.cub

Handling Special Pixels: REPLACEMENT

Description

This option specifies what special pixels will be replaced with.

Type string
Default ZEROES
Option List:
Option Brief Description
ZEROESReplace with Zeroes Replaces all special pixels with zeroes.
MINMAXReplace with max and min Replaces HRS and HIS pixels with the maximum value of the cube and LRS and LIS pixels with the minimum.

Examples

Example 1

fft example

Description

Example of the Fourier transform.

Command Line

fft from=peaks.cub magnitude=peaks_magnitude.cub phase=peaks_phase.cub
Compute the Fourier transform of peaks.cub and store the results in peaks_magnitude.cub and peaks_phase.cub

GUI Screenshot

fft GUI

Example GUI

Screenshot of GUI with parameters filled in to perform the fft application

Input Image

Input image

Input image for fft

Parameter Name: FROM

This is the input image, peaks.cub.

Output Images

Magnitude image

Example magnitude output

Parameter Name: MAGNITUDE

This is the magnitude output of the transform of peaks.cub.

Phase image

Example phase output

Parameter Name: PHASE

This is the phase output of the transform of peaks.cub.

History

Jacob Danton2005-11-28 Original version
Brendan George2006-09-28 Documentation fixes
Steven Lambright2008-05-12 Removed references to CubeInfo
Steven Lambright2008-10-16 Documentation fixes: Created images for the GUI screenshots, which were missing.
Steven Lambright2012-02-24 This program now takes advantage of multiple global processing threads.