ENVIROI::Hydrate

Use the Hydrate static function method to create the object from its dehydrated form. The dehydrated form consists of a hash containing the object’s properties and values. The Hydrate and Dehydrate methods let you store the object state in memory and restore it later.

Representing an object as a hash is necessary for running ENVI analytics with the ENVI Task Engine.

See the ENVIHydrate function if you are creating a general IDL routine that will restore multiple object types.

For additional information, see What are Hydrate and Dehydrate routines used for?

Example

; Start the application

e = ENVI(/HEADLESS)

; Open an ENVIRaster

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

SUBDIRECTORY = ['data'])

raster = e.OpenRaster(file)

; Open a multi-part ROI

ROIFile = FILEPATH('qb_boulder_roi.xml', $

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

rois = e.OpenROI(ROIFile)

; Dehydrate the first ROI

dehydratedForm = rois[0].Dehydrate()

FOREACH roi, rois DO roi.Close

; Restore the dehydrated object

newROI = ENVIROI.Hydrate(dehydratedForm)

Print, newROI, /IMPLIED_PRINT

Syntax

Result = ENVIROI.Hydrate(DehydratedForm, ERROR=value)

Return Value

The result is a reference to a new object instance of this virtual raster class.

Arguments

DehydratedForm

Key	Description
factory	Required. A string value of `ENVIROI` indicating what object type the hash represents.
url	Required. A uniform resource locator (URL) identifying an ROI file for use in ENVI processing. Example: "url" : "/usr/local/INSTALL_DIR/envi/data/qb_boulder_roi.xml"
dataset_index	This key pertains to multiple ROIs in an ROI file. Use it to define a zero-based integer index corresponding to the ROI to open. Example: "dataset_index" : 2

Key

Description

factory

Required. A string value of ENVIROI indicating what object type the hash represents.

url

Required. A uniform resource locator (URL) identifying an ROI file for use in ENVI processing. Example:

"url" : "/usr/local/INSTALL_DIR/envi/data/qb_boulder_roi.xml"

dataset_index

This key pertains to multiple ROIs in an ROI file. Use it to define a zero-based integer index corresponding to the ROI to open. Example:

"dataset_index" : 2

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.

Version History

ENVI 5.4

Introduced

API Version

4.2