GaussianStretchRaster Task

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

; Start the application

e = ENVI()

; Open an input file

File = Filepath('qb_boulder_msi', Subdir=['data'], $

Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Get the task from the catalog of ENVITasks

Task=ENVITask('GaussianStretchRaster')

; Define inputs

Task.INPUT_RASTER = Raster

Task.MIN = [180, 210, 120, 90]

Task.MAX = [800, 1300, 1055, 1100]

; Run the task

Task.Execute

; Get the collection of data objects currently available in the Data Manager

DataColl = e.Data

; Add the output to the Data Manager

DataColl.Add, Task.OUTPUT_RASTER

; Display the result

View = e.GetView()

Layer = View.CreateLayer(Task.OUTPUT_RASTER)

Syntax

Result = ENVITask('GaussianStretchRaster')

Input properties (Set, Get): BRIGHTNESS, INPUT_RASTER, MAX, MIN, OUTPUT_RASTER_URI, STDEV

Output properties (Get only): OUTPUT_RASTER

Properties marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.

Methods

This task inherits the following methods from ENVITask:

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

BRIGHTNESS (optional)

Set this property 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 (required)

Set this property 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.

MIN (required)

Set this property 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.

OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI.

OUTPUT_RASTER_URI (optional)

Specify a string with the fully qualified filename and path to export the associated OUTPUT_RASTER.

If you set this property to an asterisk symbol (*), the output raster will be virtual and not written to disk.
If you do not specify this property, or set it to an exclamation symbol (!), a temporary file will be created.

STDEV (optional)

Specify the standard deviation value for the Gaussian function. The default value is 0.3.

Version History

ENVI 5.2	Introduced
ENVI 5.5	OUTPUT_RASTER_URI now supports '*', which allows OUTPUT_RASTER to be virtual output.

API Version

4.3