ENVIBinaryGTThresholdRaster

This function constructs an ENVIRaster from an input raster where pixel values above a specified threshold are set to 1 and all others are set to 0.

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 BinaryGTThresholdRaster.

Example

; Start the application

e = ENVI()

; Open an input file

file = FILEPATH('qb_boulder_msi', ROOT_DIR=e.ROOT_DIR, $

SUBDIRECTORY = ['data'])

raster = e.OpenRaster(file)

; Set the thresholds for each band

threshold = [250, 360, 270, 360]

rasterBinaryImage = ENVIBinaryGTThresholdRaster(raster, threshold)

; save it in ENVI raster format

newFile = e.GetTemporaryFilename()

rasterBinaryImage.Export, newFile, 'ENVI'

; Open the thresholded image

rasterBinaryImage = e.OpenRaster(newFile)

; Display the result

View = e.GetView()

Layer = View.CreateLayer(rasterBinaryImage)

Layer.Quick_Stretch = 'equalization'

Syntax

Result = ENVIBinaryGTThresholdRaster(Input_Raster, Threshold, ERROR=variable])

Return Value

This routine returns a reference to an ENVIRaster whose data type is Byte.

Arguments

Input_Raster

Specify the input ENVIRaster.

Threshold

Specify an array of threshold values (one per band). If the source raster only has one band, specify an array with one element.

Methods

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

Dehydrate

Hydrate

Keywords

ERROR

Set this keyword to a named variable that will contain any error message issued during execution of this routine. If no error occurs, the ERROR variable will be set to a null string (''). If an error occurs and the routine is a function, then the function result will be undefined.

When this keyword is not set and an error occurs, ENVI returns to the caller and execution halts. In this case, the error message is contained within !ERROR_STATE and can be caught using IDL's CATCH routine. See IDL Help for more information on !ERROR_STATE and CATCH.

See Manage Errors for more information on error handling in ENVI programming.

NAME

Specify a string that identifies the raster.

Version History

ENVI 5.3	Introduced
ENVI 5.3.1	Documented the dehydrated form of this virtual raster
ENVI 5.4	Added Hydrate and Dehydrate methods; added NAME keyword

API Version

4.2