ISIS Application Documentation
sigmastretch | Printer Friendly View | TOC | Home |
Apply a Sigma Stretch to a cube.
| Overview | Parameters | Example 1 |
Description
This application is a translation of the Davinci script "sstretch" (Arizona
State University, http://davinci.asu.edu). This program will stretch a cube
according to the following formula for each pixel in the image:
new_dn = (old_dn - avg) * (variance / stddev)
where avg and stddev are the statistical average and standard
deviation of all valid pixels in the current band. The variance is a
user-specified parameter, VARIANCE, that affects how much the histogram of
the image is widened, and does not represent the statistical variance of the
image.
CategoriesRelated 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 19:28:13 |
Parameter GroupsFiles
Parameters
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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 19:28:13 |
Files: FROM
Description
The input cube to which the sigma stretch will be applied.
| Type | cube |
|---|---|
| File Mode | input |
| Filter | *.cub |
Files: TO
Description
The resultant cube containing the image after being stretched.
| Type | cube |
|---|---|
| File Mode | output |
| Pixel Type | real |
| Filter | *.cub |
Parameters: VARIANCE
Description
The nonuniformity of the output image's histogram. For values less than 1.0, the distribution will be closer to uniform. This value must be greater than 0.0.
| Type | double |
|---|---|
| Default | 40.0 |
| Minimum | 0.0 (exclusive) |
Example 1Two THEMIS Images Description
This example shows a typical usage of sigmastretch as part of THEMIS
mosaic creation. As input, the two images have very high contrast, and
as such, blending the overlapping area will result in an awkward
transition between the image bounds. By running sigmastretch first, the
resulting images have less contrast, and can be mosaicked with good
results. The default value for the VARIANCE of 40.0 here is used, as is
typical in THEMIS processing.
Command Line
sigmastretch
from=I01086005.cub to=I01086005.fx.cub;
sigmastretch from=I23851018.cub to=I23851018.fx.cub
We're running the program once for each image. Without using multiple
images, it's hard to see the differences due to "qview" automatically
stretching the image for viewing. When mosaicked, however, the
contrast is especially noticeable.
GUI Screenshot
Input Image
Output Image
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![The first sigmastretch GUI](javascript:popUpNewWindow ("assets/images/gui1.jpg",614, 750))
![The second sigmastretch GUI](javascript:popUpNewWindow ("assets/images/gui2.jpg",614, 750))
![Mosaic of unstretched input images](javascript:popUpNewWindow ("assets/images/before.jpg",512, 512))
![Mosaic showing results of the sigmastretch application](javascript:popUpNewWindow ("assets/images/after.jpg",512, 512))
| 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 |