ISIS Application Documentation
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Apply a spatial high pass filter to a cube
| Overview | Parameters | Example 1 | Example 2 |
Description
This program applies a high pass filter to a cube. That is, it filters
the cube data by suppressing low frequency data (e.g., albedo) and allows
high frequency data (e.g., structure) to pass through.
This is done by convolving an NxM boxcar through the data, where N and M
are odd integers. The average of the boxcar is subtracted from the
middle pixel. The result of the subtraction is the high frequency
information. Thus, output(i,j) = input(i,j) - average(i,j,N,M) where
i and j are the sample and line position in the cube, N and M are the
size of the boxcar, and average(i,j,N,M) is the average of the NxM centered
at i,j. A small boxcar (e.g, 3x3) will allow fine
details to pass thru and will significantly suppress the albedo. A large
boxcar (e.g, 101x101) will enhance larger features and allow more albedo
information to pass through. In general, features which are half the size
of the boxcar will pass through the filter.
CategoriesRelated Applications to Previous Versions of ISISThis program replaces the following application existing in previous versions of ISIS:
Related Objects and DocumentsApplicationsHistory
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| 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 19:28:11 |
Parameter GroupsFiles
Boxcar Settings
Options
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| 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 19:28:11 |
Files: TO
Description
The resultant filtered cube
| Type | cube |
|---|---|
| File Mode | output |
| Pixel Type | real |
Boxcar Settings: SAMPLES
Description
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 |
Boxcar Settings: LINES
Description
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 Settings: MINOPT
Description
This parameter determines whether the minimum parameter is to be interpreted as a count of pixels, or a percentage of all pixels in the boxcar.
| Type | string | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Default | COUNT | |||||||||
| Option List: |
|
Boxcar Settings: MINIMUM
Description
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 | double |
|---|---|
| Default | 1 |
| Minimum | 1 (inclusive) |
Options: 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 boxcar statistics.
| Type | double |
|---|---|
| Internal Default | Use all pixels |
| Less Than | HIGH |
Options: 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 boxcar statistics.
| Type | double |
|---|---|
| Internal Default | Use all pixels |
| Greater Than | LOW |
Options: PROPAGATE
Description
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 |
Options: ADDBACK
Description
This option is used to specify how much of the input pixel is added to the filter result. A value of 100 implies the entire input pixel will be added back to the filter which is equivalent to the sharpen program. Recall that highpass filters suppress albedo and therefore you are essentially selecting a percentage of albedo to addback.
| Type | double |
|---|---|
| Default | 0.0 |
| Minimum | 0.0 (inclusive) |
| Maximum | 100.0 (inclusive) |
Example 17 by 7 Description Use a 7 by 7 pixel filter and use all pixels.
Command Line
highpass from=2400r to=2400r.hpf7x7all samp=7 line=7
The highpass box filter is selected 7 pixels wide by 7 pixels long and parameters 'low' and 'high' default to 'use all pixels'.
GUI Screenshot
Input Image
Output Image
|
![highpass GUI](javascript:popUpNewWindow ("assets/image/highpass7x7allGui.jpg",480, 415))
![Input image](javascript:popUpNewWindow ("assets/image/2400r.jpg",500, 500))
![Output image showing results of the highpass application with 7 by 7 pixel filter.](javascript:popUpNewWindow ("assets/image/2400r.hpf7x7all.jpg",500, 500))
| 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 19:28:11 |
Example 221 by 21 Description Use a 21 by 21 pixel filter and use all pixels.
Command Line
highpass from=2400r to=2400r.hpf21x21all samp=21 line=21
The boxcar filter is selected 21 pixels wide by 21 pixels long and parameters 'low' and 'high' default to 'use all pixels'.
GUI Screenshot
Input Image
Output Image
|
![highpass GUI](javascript:popUpNewWindow ("assets/image/highpass21x21allGui.jpg",480, 415))
![Output image showing results of the highpass applica tion with 21 by 21 pixel filter.](javascript:popUpNewWindow ("assets/image/2400r.hpf21x21all.jpg",500, 500))
| 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 19:28:11 |