ISIS Application Documentation

reduce

Printer Friendly View | TOC | Home

Reduce the pixel dimensions of an image

Overview

Parameters

Example 1

Example 2

Description

This program reduces a cube to a given proportion of the original or to specific pixel dimensions.

The reduction method options include either averaging the pixels (AVERAGE) or selecting the closest pixel at the window center (NEAREST) when generating a sub-sampled cube. More information is included under the Parameter Group headings.

For Level1:

All keywords in the input file label are propagated to the output file
An AlphaCube group with the original size is created in the output cube labels
Coordinates returned in qview are accurate if SPICE kernels are present in the labels

For Level2 or Mosaic:

The Scale and PixelResolution are recomputed if SSCALE and LSCALE are equal
The Mapping Group is removed if SSCALE and LSCALE are not equal
Coordinates are returned in qview only if the Mapping group was propagated
Use the same value for SSCALE and LSCALE if the reduced cubes will be mosaicked together

Use the ONS and ONL parameters with caution because the scaling factor for the samples and lines may be different in the output cube. Within this application, special pixels are considered invalid and will be replaced depending on the settings for VALIDPER and VPER_REPLACE parameters.

History

Jeff Anderson	1995-11-06	Original version
Tracie Sucharski	2002-10-12	Ported to Isis 3.0, Separated magcube into reduce and enlarge.
Tracie Sucharski	2003-05-13	Read in ons/onl as integers not doubles.
Stuart Sides	2003-05-16	Modified schema location from astrogeology... to isis.astrogeology..."
Stuart Sides	2003-07-29	Modified filename parameters to be cube parameters where necessary
Jeff Anderson	2004-07-14	Fixed propagation bug
Tracie Sucharski	2004-07-15	Forget to change ons/onl minimum inclusive values from 1.0 to 1 during the 2003-5-13 change.
Drew Davidson	2005-08-17	Added example
Tracie Sucharski	2006-04-03	Fixed bug in average algorithm, forgot to divide Vper by 100.
Jeff Anderson	2006-09-19	Fixed problems when program ran in batchlist
Sean Crosby	2007-02-28	Program now updates output file's mapping keywords
Steven Koechle	2008-01-23	Changed so if it failed VPER the output cube would get null values. Now processes cube bands from user input correctly
Steven Lambright	2008-05-13	Removed references to CubeInfo
Steven Koechle	2008-05-15	Added radio button for VPER options to allow original functionality.
Steven Lambright	2008-12-22	The "Scale" keyword in the Projection group in the labels is now being updated if this program is run on a projected cube.
Mackenzie Boyd	2009-09-03	Added keyword REDUCTION_TYPE to allow for clear switching between ons, onl and sscale, lscale. Fixed problem involving cube remaining open after an exception.
Janet Barrett	2009-10-22	Now uses the SubArea class to produce output cube labels with corrected Mapping, Instrument, and AlphaCube groups.
Travis Addair	2009-11-12	Improved documentation, changed parameter names, and updated examples.
Travis Addair	2009-12-09	Updated documentation and changed parameters STOTAL and LTOTAL back to ONS and ONL, respectively.
Sharmila Prasad	2011-04-26	Ported the reduce by near and average functionality from the app to base/objs/Reduce class
Sharmila Prasad	2011-10-07	Fixed bug #0000463 regarding memory leak
Sharmila Prasad	2012-02-01	Fixed bug #0000681 - reduce in ISIS 3.3.0 is ignoring the +N band identifier
Tracie Sucharski	2013-01-16	Fixed an intermittent bug which caused a round off error which resulted in the output bands beyond band 1 being all NULL. Fixes #1385.
Ella Mae Lee	2013-11-06	Updated the documentation and fixed incorrect information. Fixes #1691.

U.S. Department of the Interior | U.S. Geological Survey
ISIS | Privacy & Disclaimers | Astrogeology Research Program
To contact us, please post comments and questions on the USGS Astrogeology Discussion Board
To report a bug, or suggest a feature go to: ISIS Github
File Modified: 02/21/2025 19:28:13

Parameter Groups

Files

Name	Description
FROM	Input cube to reduce
TO	Output cube

Scaling Parameters

Name	Description
ALGORITHM	Reduction method algorithm (Average, Nearest-Neighbor)
MODE	Image reduction mode (SCALE or TOTAL)
SSCALE	Sample scaling factor inverse
LSCALE	Line scaling factor inverse
ONS	Number of samples in output
ONL	Number of lines in output
VALIDPER	Valid percentage
VPER_REPLACE	Replacement method when VALIDPER is not met

Files: FROM

Description

Use this parameter to select the filename. All bands within the file will be scaled down.

Type	cube
File Mode	input
Filter	*.cub

Close Window

Files: TO

Description

This file will contain the results of the reduced cube. The output cube may not have all the keywords propagated to the output file depending on the reduction method chosen, and the type of input file.

Type	cube
File Mode	output
Filter	*.cub

Close Window

Scaling Parameters: ALGORITHM

Description

Select the algorithm to use to reduce the image. The AVERAGE option will compute the output value by averaging the input pixels. The NEAREST option will assign the input pixel that is closest to the center of the window being analyzed as the output value.

Type

string

Default

AVERAGE

Option List:

Option	Brief	Description
AVERAGE	Average surrounding pixels	Use pixel averaging to reduce the image.
NEAREST	Nearest-Neighbor	Use the nearest-neighbor algorithm to reduce the image.

Close Window

Scaling Parameters: MODE

Description

Select between reducing the image to a proportion of the original (use a scaling factor inverse) or to specific pixel dimensions (define total number of pixels).

Type

string

Default

SCALE

Option List:

Option

Brief

Description

SCALE

Reduce by a scaling factor inverse

Reduces the input image by a scaling factor inverse. The scaling factor inverse must be specified in the SSCALE and LSCALE parameters, respectively.

Exclusions

Inclusions

SSCALE
LSCALE

TOTAL

Reduce to specified pixel dimensions (samples, lines)

Reduces the input image to a total number of pixels. The number of pixels in the output image must be specified in the ONS and ONL parameters, respectively.

Exclusions

SSCALE
LSCALE

Type

string

Default

NULL

Option List:

Option	Brief	Description
NULL	NULL replacement	Assign a NULL value when VALIDPER is not met.
NEAREST	Nearest-Neighbor replacement	Use the nearest-neighbor algorithm to assign a value when VALIDPER is not met. The output pixel will be set to the input pixel which is closest to the center of the window being analyzed.

Close Window

Example 1

Reduce the image using different scale factor inverse

Description

In this example, the sample scale factor inverse is 2 (sscale=2) and no other parameter is entered. This implies that the default settings will be used for all the parameters except for sscale. The number of samples will be scaled down by a factor of 2, not scaled up. There will be no reduction in the number of lines because nothing was entered for lscale, and "lscale=1" is the default. Since the default mode of reduction is "SCALE," the mode parameter does not need to be specified.

Command Line

reduce from=peaks.cub to=reducedPeaks.cub sscale=2.0

In this example, the image will be scaled down by a factor of 2, not scaled up. No reduction in the lines will be made. The pixels that do not meet the VALIDPER setting will be set to NULL in the output file.

GUI Screenshot

GUI for REDUCE

Example GUI

Screenshot of the GUI with parameters set to perform a reduction of the input image. The default setting "algorithm=average mode=scale lscale=1 validper=50 vper_replace=NULL" will be used.

Input Image

The input image before reduction.

Input image for the reduce application

Parameter Name: FROM

This is the input image that will be reduced.

Output Image

The image after reduction.

Output image from the reduce application

Parameter Name: TO

This is the reduced image. Though it has been scaled down so that it can be viewed in a web browser, the essential change can still be observed. The distortion is noticeable because the output file has been reduced in the sample direction but not in the line direction. The output image is half as wide as the input image but is the same height, and the features are compressed in one direction.

Example 2

Reduce the image using the pixel dimensions

Description

Reduce the image by setting the number of samples to 150, and the number of lines to 250. The parameter Mode must be set to "Total" when the ONS and ONL parameters are used.

Command Line

reduce from=peaks.cub to=totalPeaks.cub mode=total ons=150 onl=250

In this example, the input image will be reduced to specific pixel dimensions. The parameter "mode" is set to "total" and the default settings will be used for the remaining parameters.

GUI Screenshot

GUI for REDUCE

Example GUI

Screenshot of the GUI with parameters set to perform a sample and line reduction to a total number of pixels. The default settings for "algorithm," "validper," and "vper_replace" will be used.

Input Image

The input image before reduction.

Input image for reduce application

Parameter Name: FROM

This is the image that will be reduced.

Output Image

The image after reduction.

Output image from the reduce application

Parameter Name: TO

This is the reduced image. Though it has been scaled down so that it can be viewed in a web browser, the essential change can still be observed. The distortion is noticeable because the output cube is not as wide as the input cube, and the features are compressed in one direction. The output cube has 1/3 the number of samples and 1/2 the number of lines as the input cube.

Quick Links

Documentation Versions

reduce

Description

Categories

History

Parameter Groups

Files

Scaling Parameters

Files: FROM

Description

Files: TO

Description

Scaling Parameters: ALGORITHM

Description

Scaling Parameters: MODE

Description

Exclusions

Inclusions

Exclusions

Inclusions

Scaling Parameters: SSCALE

Description

Scaling Parameters: LSCALE

Description

Scaling Parameters: ONS

Description

Scaling Parameters: ONL

Description

Scaling Parameters: VALIDPER

Description

Scaling Parameters: VPER_REPLACE

Description

Example 1

Description

Command Line

GUI Screenshot

Input Image

Output Image

Example 2

Description

Command Line

GUI Screenshot

Input Image

Output Image