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.
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.
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.
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.
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.
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
ONS
ONL
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.
This parameter specifies what percentage of the pixels need to be
valid (non-special pixels) to determine the output value based on
the reduction method chosen. For example, scaling down by a factor
of two results in a 2x2 window (four pixels) being reduced to one
pixel. If VALIDPER is set to 50, then at least two of the
four pixels (50%) must be valid. If this criterion is met,
then the result
is derived using the valid input pixels based on the chosen
algorithm. Otherwise, the output pixel is assigned a NULL value by
default or the closest pixel if "NEAREST" is chosen for VPER_REPLACE.
This parameter specifies the method to use when the value specified
for VALIDPER is not met. The resultant pixel will be filled based on
whether NULL or NEAREST is chosen for this parameter. The default
is to replace with a NULL value if nothing is defined by the user.
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.
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.
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.
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.
