ENVIGridDefinition::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)

; 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

Syntax

Result = ENVIGridDefinition.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 `GridDefinition` indicating what object type the hash represents.
coord_sys	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.
extents	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. Example: "extents" : [257017.6, 7831362.4, 1153892.7, 7270425.0]
nrows	Required. The number of rows in the grid. Example: "nrows" : 1024
ncolumns	Required. The number of columns in the grid. Example: "ncolumns" : 1024

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