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?


; Start the application
; Open an input file
File = Filepath('bhtmref.img', Subdir=['classic', 'data'], $
Raster = e.OpenRaster(File)
; Specify the gains and offsets
Gains = [2.00, 1.33, 1.20, 1.11, 2.60, 3.12]
Offsets = [12.33, 1.10, 6.00, 1.55, 5.32, 4.05]
GainOffsetImage = ENVIGainOffsetRaster(Raster, Gains, Offsets)
; Retrieve the dehydrated hash
dehydratedForm = GainOffsetImage.Dehydrate()
; Restore the object
newImage = ENVIGainOffsetRaster.Hydrate(dehydratedForm)
Print, newImage, /IMPLIED_PRINT


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

Return Value

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






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


Required. The input ENVIRaster for use in ENVI processing.


"input_raster": {
    "url": "/usr/local/INSTALL_DIR/envi/classic/data/bhtmref.img",
    "factory": "URLRaster"


Required. A double-precision array of data gain values (one per band) to apply to the input raster. Example:

"gain": [2.0, 1.33, 1.2, 1.11, 2.6, 3.12],


A string that identifies the raster.


Required. A double-precision array of data offset values (one per band) to apply to the input raster. Example:

"offset" : [12.33, 1.10, 6.00, 1.55, 5.32, 4.05]


ERROR (optional)

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


API Version


See Also

ENVIGainOffsetRaster, ENVIGainOffsetRaster::Dehydrate, ENVIHydratable, ENVIHydrate