ENVIROI::AddThreshold

The AddThreshold method adds a band threshold definition to an ROI.

Example

; Launch the application

e = ENVI()

; Open the input file

file = Filepath('qb_boulder_msi', ROOT_DIR=e.Root_Dir, $

SUBDIRECTORY=['data'])

raster = e.OpenRaster(file)

view = e.GetView()

layer = view.CreateLayer(raster)

; Define a new ROI with a threshold and display it

roi = EnviRoi(NAME='Threshold', COLOR='Blue')

roi.AddThreshold, raster, 3, MIN_VALUE=0, MAX_VALUE=175

roiLayer = layer.AddRoi(roi)

Syntax

ENVIROI.AddThreshold, Raster, Band [, Keywords=value]

Arguments

Raster

The ENVIRaster reference that contains the band of data used for applying the given threshold range.

Band

An integer value specifying which band of the ENVIRaster to use. The valid range of values is 0 to numBands-1. Bands are zero-based, so 0=Band 1, 1=Band 2, etc.

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.

MIN_VALUE

Set this keyword to specify the minimum data value to include in the threshold range. If the MIN_VALUE keyword is not set, then the threshold will include all the data values from the band that are less than or equal to the MAX_VALUE.

Note: You must set either the MIN_VALUE or MAX_VALUE keyword, or both.

MAX_VALUE

Set this keyword to specify the maximum data value to include in the threshold range. If the MAX_VALUE keyword is not set, then the threshold will include all the data values from the band that are greater than or equal to the MIN_VALUE.