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svfilter

Apply a variance or standard deviation filter to a cube

This program applies either a variance or standard deviation filter to a cube. The standard deviation filter is simply the square root of the variance and is selected by setting the FILTER parameter to STDDEV.

Related Applications to Previous Versions of ISIS

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

boxfilter

History

Eric Eliason	1988-05-20	Original version
Tracie Sucharski	2002-08-13	Ported to Isis 3.0
Jeff Anderson	2002-11-26	Fixed bug which disallowed the standard deviation filter
K Teal Thompson	2002-12-03	Add examples.
K Teal Thompson	2003-03-28	Make images smaller.
Stuart Sides	2003-04-04	Fixed problem with isiscvs not checking in the thumb and image directories.
Kim Sides	2003-05-13	Added application test
Stuart Sides	2003-05-16	Modified schema location from astogeology... to isis.astrogeology..."
Stuart Sides	2003-07-29	Modified filename parameters to be cube parameters where necessary

Parameters

Files

Input cube to filter

Type	cube
File Mode	input
Filter	*.cub

The resultant filtered cube

Type	cube
File Mode	output
Pixel Type	real

Filter Type

The output of the filter operation is either the variance value or the standard deviation value.

Type

string

Default

VARIANCE

Option List:

Option	Brief	Description
VARIANCE	Perform variance filter	This will output the variance at the center of the boxcar.
STDDEV	Perform standard deviation filter	This will output the standard deviation at the center of the boxcar.

Boxcar Size

This is the total number of samples in the boxcar. It must be odd and can not exceed twice the number of samples 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

This is the total number of lines in the boxcar. It must be odd and can not exceed twice the number of lines 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 Restrictions

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 boxcar statistics.

Type	double
Internal Default	Use all pixels
Less Than	HIGH

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 boxcar statistics.

Type	double
Internal Default	Use all pixels
Greater Than	LOW

This is the minimum number of valid pixels which must occur inside the NxM boxcar for filtering to occur. For example, 3x5 boxcar has 15 pixels inside. If MINIMUM=10 then the filter will occur if there are 10 or greater valid pixels. A valid pixel is one that is not special (NULL, LIS, etc) and is in the range defined by LOW to HIGH.

Type	integer
Default	1
Minimum	1 (inclusive)

Special Pixels

This option is used to define how special pixels are handled. If the center pixel of the boxcar is a special pixel it will be propagated or set to NULL depending on the value of this parameter.

Type	boolean
Default	TRUE

Example 1

run svfilter

This example shows an svfilter operation using standard deviation.

Command Line

svfilter a Terra image. Use STDDEV filter (fi=s)

svfilter  fr=../IN/peaks.cub:4 t=OUT/svfilter.sd fi=s s=5 li=5

GUI Screenshot

Example Gui

svfilter Gui

Screenshot of GUI with parameters filled in to perform an svfilter operation on the input image.

Input Image

Input image for svfilter

Input image

Parameter Name: FROM

This is the input image for the svfilter examples.

Output Image

Output image for svfilter

Output image showing results of the svfilter application.

Parameter Name: TO

This is the output image that results from STDDEV filter.

Example 2