ENVIStretchParameters::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 input file

File = Filepath('bhdemsub.img', $

Subdir=['classic', 'data'], $

Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Set the DEM stretch parameters

DEMStretch = ENVIStretchParameters( $

STRETCH_TYPE='Square Root', $

MIN_VALUE=1241, $

MAX_VALUE=1503)

; Retrieve the dehydrated hash

dehydratedForm = DEMStretch.Dehydrate()

; Restore the object

newStretch = ENVIStretchParameters.Hydrate(dehydratedForm)

Print, newStretch, /IMPLIED_PRINT

Syntax

Result = ENVIStretchParameters.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 `StretchParameters` indicating what object type the hash represents.
maxPercent	Optional. A value from 0 to 100 indicating the maximum percentage of the histogram to include in the specified stretch. If you do not set this key, the default value will be 100. Example: "maxPercent": 82
maxValue	Optional. A double-precision floating point value indicating the maximum pixel value for the specified stretch. If you do not set this key, the default value will be `NaN`. Example: "maxValue": 1503.0000
minPercent	Optional. A value from 0 to 100 indicating the minimum percentage of the histogram to include in the specified stretch. If you do not set this key, the default value will be 0. Example: "minPercent": 0.0
minValue	Optional. A double-precision floating point value indicating the minimum pixel value for the specified stretch. If you do not set this key, the default value will be `NaN`. Example: "minValue": 1241.000
stretchType	Optional. A string indicating the stretch type to apply to a single-band raster. Example: "stretchType": "Square Root"

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 5.5.1

Introduced

API Version

4.2