SpectralIndex Task

This task creates a spectral index raster from one pre-defined spectral index. Spectral indices are combinations of surface reflectance at two or more wavelengths that indicate relative abundance of features of interest.

Use the SpectralIndices task to create a raster with one or more bands, where each band represents a different spectral index.

The data-ignore value of the output raster is set to -10³⁴.

The virtual raster associated with this task is ENVISpectralIndexRaster.

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('SpectralIndex')

; Define inputs

Task.INDEX = 'Normalized Difference Vegetation Index'

Task.INPUT_RASTER = Raster

; 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('SpectralIndex')

Input parameters (Set, Get): INDEX, INPUT_RASTER, OUTPUT_RASTER_URI

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

INDEX (required)

Specify a string representing the pre-defined spectral index to apply to the input raster:

INPUT_RASTER (required)

Specify a raster from which to generate a spectral index 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.