ISIS Application Documentation
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Filter a cube through a kernel using Gaussian weight
| Overview | Parameters | Example 1 | Example 2 |
Description
This program calculates weight based on the bell-shaped Gaussian
curve. The weight is then applied to an image kernel in such a way as to
create a filter that will move a weighted average through the image. The
end result is a blurred image with reduced detail and noise. The Gaussian
function that determines the weight for all of the values in the kernel is
as follows
/ x^2+y^2 \
- | ----------- |
G(x,y) = 1 \ 2(STDDEV)^2 /
--------------- e^
2(pi)(STDDEV)^2
This formula creates a kernel that then runs through the image. The center of
the kernel is at (0,0). This means that a 3x3 boxcar will be of the form
The kernel coordinates
(-2,-2) (-1,-2) (0,-2) (1,-2) (2,-2)
(-2,-1) (-1,-1) (0,-1) (1,-1) (2,-1)
(-2, 0) (-1, 0) (0, 0) (1, 0) (2, 0)
(-2, 1) (-1, 1) (0, 1) (1, 1) (2, 1)
(-2, 2) (-1, 2) (0, 2) (1, 2) (2, 2)
The kernel values (approx)
1 4 7 4 1
4 16 26 16 4
7 26 41 26 7 x 1/273
4 16 26 16 4
1 4 7 4 1
CategoriesRelated Objects and DocumentsApplicationsHistory
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Parameter GroupsFiles
boxcar
Standard Deviation
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Files: FROM
Description
Use this parameter to select the filename. All bands within the file will be filtered.
| Type | cube |
|---|---|
| File Mode | input |
| Filter | *.cub |
Files: TO
Description
This file will contain the results of the filter, a blurred version of the input file.
| Type | cube |
|---|---|
| File Mode | output |
boxcar: SIZE
Description
This is the user specified size of the boxcar that will move through the image. The boxcar must be square, so the default value of 3 will result in a 3 x 3 boxcar. A value of five would result in a 5 x 5 boxcar moving through the image.
| Type | integer |
|---|---|
| Default | 3 |
| Odd | This value must be an odd number |
Standard Deviation: STDDEV
Description
At the most basic level, standard deviation can be thought of in this context as the intensity of the blur being applied to the image. The higher this value, the more noise and detail will be removed. At a deeper level, standard deviation is described as the average distance from any single measurement of a set to the mean of that set.
| Type | double |
|---|---|
| Default | 1.0 |
| Minimum | 0 (exclusive) |
Example 1Using a 3 x 3 boxcar Description
This example shows the use of the default standard deviation (1.0) and the
default boxcar size (3). Since the boxcar must be square in this program,
this means that a 3 x 3 boxcar will be used.
Command Line
gauss
from= peaks.cub
to=gauss3x3.cub
size=3
STDDEV= 1.0
This example uses all of the default values specified by the program
GUI Screenshot
Input Image
Output Image
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Example 2Using a 5 x 5 boxcar Description
This example shows the use of a larger standard deviation (2.0) and the
larger boxcar (5). As with the last example, the single value of 5 will
be applied to both the line size and sample size of the boxcar.
Command Line
gauss
from= peaks.cub
to=bigblur.cub
size=5
STDDEV= 2.0
This example will create a more dramatic blur, as everything is larger
than in the first example
GUI Screenshot
Input Image
Output Image
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