This task accepts a source raster and returns a raster with a Gaussian stretch applied.
ENVI performs the following steps to compute a Gaussian stretch:
- Sets the data mean value to a screen value of 127.
- Sets the data value that is three standard deviations below the mean value to a screen value of 0.
- Sets the data value that is three standard deviations above the mean value to a screen value of 255.
Intermediate values are assigned screen values using a Gaussian curve.
The virtual raster associated with this task is ENVIGaussianStretchRaster.
Example
e = ENVI()
File = Filepath('qb_boulder_msi', Subdir=['data'], $
Root_Dir=e.Root_Dir)
Raster = e.OpenRaster(File)
Task=ENVITask('GaussianStretchRaster')
Task.INPUT_RASTER = Raster
Task.MIN = [180, 210, 120, 90]
Task.MAX = [800, 1300, 1055, 1100]
Task.Execute
DataColl = e.Data
DataColl.Add, Task.OUTPUT_RASTER
View = e.GetView()
Layer = View.CreateLayer(Task.OUTPUT_RASTER)
Syntax
Result = ENVITask('GaussianStretchRaster')
Input parameters (Set, Get): BRIGHTNESS, INPUT_RASTER, MAX, MIN, OUTPUT_RASTER_URI, STDEV
Output parameters (Get only): OUTPUT_RASTER
Parameters marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Parameters marked as "Get" are those whose values you can retrieve but not set.
Input Parameters
BRIGHTNESS (optional)
Set this parameter to an integer value from 0 to 100, indicating the brightness level to display. The default value is 50 if no brightness is specified. You can also set this value to a scalar or an array with the same number of elements as the raster has bands.
INPUT_RASTER (required)
Specify a raster on which to apply the stretch.
MAX (optional)
Set this parameter to the maximum value to be considered, also known as the "white point." If the value is a scalar, it applies to all bands. If it is an array, it must have the same number of elements as the input raster has bands. If not set, this value will be calculated from the input raster.
MIN (optional)
Set this parameter to the minimum value to be considered, also known as the "black point." If this value is a scalar, it applies to all bands. If it is an array, it must have the same number of elements as the input raster has bands. If not set, this value will be calculated from the input raster.
OUTPUT_RASTER_URI (optional)
Specify a string with the fully qualified filename and path to export the associated OUTPUT_RASTER.
- If you set this parameter to an asterisk symbol (*), the output raster will be virtual and not written to disk.
- If you do not specify this parameter, or set it to an exclamation symbol (!), a temporary file will be created.
- If you set it to the hash symbol (#), ENVI creates a file in the temporary directory, but this file will not be deleted when ENVI closes.
STDEV (optional)
Specify the standard deviation value for the Gaussian function. The default value is 0.3.
Output Parameters
OUTPUT_RASTER
This is a reference to the output raster of filetype ENVI.
Methods
Execute
Parameter
ParameterNames
Properties
DESCRIPTION
DISPLAY_NAME
NAME
REVISION
TAGS
Version History
ENVI 5.2 |
Introduced |
ENVI 5.5 |
OUTPUT_RASTER_URI now supports '*', which allows OUTPUT_RASTER to be virtual output.
|
See Also
ENVITask, ENVIGaussianStretchRaster, ENVIRasterStatistics, Masking Support in ENVITasks