Home
About ISIS
Support
Download

ISIS 3

Documentation
Tutorials
Technical Documents

ISIS 2

Documentation
Tutorials
Technical Documents
USGS

ISIS 3 Application Documentation

specdivfilter

Standard View | TOC | Home

Apply a spectral division filter

Description
Categories
Groups
Examples
History

Description

This program applies a spectral division filter to a cube. A spectral filter works between bands as opposed to a spacial operation on a single band. As a division filter, it divides the original pixel by the average.

Categories

Related Applications to Previous Versions of ISIS

This program replaces the following application existing in previous versions of ISIS:

Related Objects and Documents

Applications

Parameter Groups

Files

Name Description
FROM Input file
TO Filtered output cube

Boxcar Size

Name Description
BANDS Number of bands in boxcar

Boxcar Settings

Name Description
LOW Minimum valid DN
HIGH Maximum valid DN

Files: FROM

Description

Input cube to filter

Type cube
File Mode input
Filter *.cub

Files: TO

Description

The resultant filtered cube

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

Boxcar Size: BANDS

Description

This is the total number of bands in the boxcar. It must be odd and can not exceed twice the number of bands in the cube. In general, the size of the boxcar does not cause the program to operate significantly slower.

Type integer
Minimum 1 (inclusive)
Odd This value must be an odd number

Boxcar Settings: LOW

Description

Valid minimum pixel value that will be used in boxcar computation. If a pixel value is less than LOW then it will not be used when computing the average.

Type double
Internal Default Use all pixels
Less Than
  • HIGH

Boxcar Settings: HIGH

Description

Valid maximum pixel value that will be used in boxcar computation. If a pixel value is greater than HIGH then it will not be used when computing the average.

Type double
Internal Default Use all pixels
Greater Than
  • LOW

Examples

Example 1

Example of usage of the spectral division filter.

Description

This example shows a spectral division filter being applied to the image with a 15 depth boxcar. This cube has 256 bands so 15 is relatively small. No averaging is done between bands, the divisoin filter more increases differences between bands. Here is an image which highlights which pixels a single pass would influence. The image shows a 9x9 dot instead of a single pixel highlighted to make it more visible. In this picture the boxcar would be seven or more bands, with the output pixel being one of the visible pixels. Depending on how large the boxcar was many of the values taken in could not be original, at a minimum, one value will be mirrored since there are only six available bands.

Command Line

specdivfilter from=/work1/mboyd/CM_1514302573_1.cub to=/work1/mboyd/postlow.cub bands=15
This example will filter the image using 15 bands and no limits on high or low.

GUI Screenshot

This program's GUI

Example GUI

Screenshot of the GUI with parameters set to perform the specdivision filter with a 15 band boxcar on the image CM_1514302573_1.ir.cub.

Input Image

The image graph before the filter

Input image spectral graph before specdivfilter

Parameter Name: FROM

This is the spectral plot of the center point of the image, (32, 32), and shows all bands, 1- 256. No filter has been applied, and the graph clearly shows how the value of line 32 sample 32 differs from band to band.

Output Image

The image graph after the filter

Output image spectral graph after being filtered

Parameter Name: TO

This is the image after the filter. First note the change in scale, everything has been amplified. Even in the apparent flat area small differences have been amplified.

Example 2

Example of usage of the spectral division filter.

Description

This example shows a spectral division filter being applied to the image with a 61 depth boxcar. This cube has 256 bands so 61 takes in over a fifth. In this case an image begins to show through, however, this is not because of average but because of amplificatino of differences from the original.

Command Line

specdivfilter from=/work1/mboyd/CM_1514302573_1.cub to=/work1/mboyd/postlow.cub bands=61
This example will filter the image using 61 bands and no limits on high or low.

GUI Screenshot

This program's GUI

Example GUI

Screenshot of the GUI with parameters set to perform the spechighpass filter with a 61 band boxcar on the image CM_1514302573_1.ir.cub.

Input Image

The image graph before the filter

Input image spectral graph before spectral division filter

Parameter Name: FROM

This is the spectral plot of the center point of the image, (32, 32), and shows all bands, 1- 256. No averaging or amplification has been applied.

Output Image

The image graph after the filter

Output image spectral graph after being filtered

Parameter Name: TO

This is the image after the filter. The amplification is clear immediately from the change in scale necessary to show the new values. All differences have been amplified, but smaller differences have increased more significantly than large differences.

History

Stacy Alley2008-09-02 Original version
Mackenzie Boyd2009-06-05 Modified documentation, added error checking for the number of bands, and added examples