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
; Create an ENVIGridDefinition object
CoordSys = ENVICoordSys(COORD_SYS_CODE=20354)
; Create a grid definition
; [xmin, ymax, xmax, ymin]
; x is easting and y is northing
Grid = ENVIGridDefinition(CoordSys, $
  EXTENT=[257017.6D, 7831362.4D, 1153892.7D, 7270425.0D], $
  NROWS=561, NCOLUMNS=897)
; Retrieve the dehydrated hash
dehydratedForm = Grid.Dehydrate()
; Restore the object
newGrid = ENVIGridDefinition.Hydrate(dehydratedForm)
Print, newGrid, /IMPLIED_PRINT


Result = ENVIGridDefinition.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 GridDefinition indicating what object type the hash represents.


Required. An ENVICoordSys object that indicates the coordinate system of the grid definition. Example:

"coord_sys" : {
   "factory" : "CoordSys",
   "coord_sys_code" : 20354

See ENVICoordSys::Dehydrate for more information.


Required. The geographic extent of the grid as follows:

[xmin, ymax, xmax, ymin]

where x and y are map coordinates (x=eastings, y=northings) or geographic coordinates (x=longitude, y=latitude), depending on the coordinate system.

The coordinates must be in the same units (degrees, meters, feet, etc.) as the associated coordinate system.

Use the extents key in conjunction with nrows and ncolumns.


"extents" : [257017.6, 7831362.4, 1153892.7, 7270425.0]


Required. The number of rows in the grid. Example:

"nrows" : 1024


Required. The number of columns in the grid. Example:

"ncolumns" : 1024



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

ENVIGridDefinition, ENVIGridDefinition::Dehydrate, ENVIHydratable, ENVIHydrate