ENVIRootStretchRaster

This function constructs an ENVIRaster from a source raster that has a root stretch applied. With this type of stretch, ENVI calculates the square root of the input histogram and applies a linear stretch.

The result is a virtual raster, which has some additional considerations with regard to methods and properties. See Virtual Rasters for more information, including how they differ from ENVITasks.

The equivalent task is RootStretchRaster.

Example

; Start the application

e = ENVI()

; Open a file

filename = FILEPATH('qb_boulder_msi', $

ROOT_DIR=e.ROOT_DIR, SUBDIRECTORY = ['data'])

raster = e.openraster(filename)

; Create the stretch raster

stretchRaster = ENVIRootStretchRaster(raster, $

MIN=[138,154,92,52], MAX=[1492,2047,1785,1807], ROOT_INDEX=2.0)

; Display the results

view = e.GetView()

layer = view.CreateLayer(stretchRaster)

Syntax

Result = ENVIRootStretchRaster(Input_Raster [, Keywords=value])

Return Value

This routine returns an ENVIRaster that has had a Root stretch applied.

Arguments

Input_Raster

Specify the input ENVIRaster.

Methods

This virtual raster inherits methods and properties from ENVIRaster; however the following methods will override the ENVIRaster methods:

Dehydrate

Hydrate

Keywords

BRIGHTNESS (optional)

Set this keyword 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.

MIN (required)

Set this keyword 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.

MAX (required)

Set this keyword 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.

NAME

Specify a string that identifies the raster.

ROOT_INDEX (optional)

If this keyword is specified, the root index function is applied to the stretch. For example, a value of 2.0 indicates a square root, and a 3.0 value indicates a cube root. If not specified, 2.0 is the default.

Version History

ENVI 5.2	Introduced
ENVI 5.3.1	Documented the dehydrated form of this virtual raster
ENVI 5.4	Added Dehydrate and Hydrate methods; added NAME keyword

API Version

4.2