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 and the ENVI Services Engine.

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

Example

; Start the application

e = ENVI()

; Open a Sentinel-2 scene

file = '20150813T102406.xml'

raster = e.OpenRaster(file)

; Get the 10-meter band group

bands10m = raster[0]

; Get the 20-meter band group

bands20m = raster[1]

; Get the 60-meter band group

bands60m = raster[2]

; Get the spatial reference of the thermal band raster

; since it has the coarsest spatial resolution (60 m)

spatialRef = bands60m.SPATIALREF

nCols = bands60m.NCOLUMNS

nRows = bands60m.NROWS

coordSysString = spatialRef.COORD_SYS_STR

coordSys = ENVICoordSys(COORD_SYS_STR=coordSysString)

pixelSize = spatialRef.PIXEL_SIZE

tiePointMap = spatialRef.TIE_POINT_MAP

tiePointPixel = spatialRef.TIE_POINT_PIXEL

; Create a grid definition

Grid = ENVIGridDefinition(coordSys, $

  PIXEL_SIZE=pixelSize, $

  TIE_POINT_MAP=tiePointMap, $

  TIE_POINT_PIXEL=tiePointPixel, $

  NCOLUMNS=nCols, $

  NROWS=nRows)

; Create a layer stack

layerStack = ENVILayerStackRaster([bands10m, $

  bands20m, bands60m], $

  GRID_DEFINITION=Grid)

; Retrieve the dehydrated hash

dehydratedForm = layerStack.Dehydrate()

layerStack.close

; Restore the object

newImage = ENVILayerStackRaster.Hydrate(dehydratedForm)

Print, newImage, /IMPLIED_PRINT

Syntax

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

Return Value

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

Arguments

DehydratedForm

"input_rasters": [
{

  "factory" : "URLRaster",

  "dataset_name" : "multispectral",

  "dataset_index" : 0,

  "url" : "/usr/local/data/landsat8_MTL.txt"

},

{

  "factory" : "URLRaster",

  "dataset_name" : "cirrus",

  "dataset_index" : 2,

  "url" : "/usr/local/data/landsat8_MTL.txt"

},

{

  "factory" : "URLRaster",

  "dataset_name" : "thermal",

  "dataset_index" : 3,

  "url" : "/usr/local/data/landsat8_MTL.txt"

}]

Keywords

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

API Version

3.1.0

See Also

ENVILayerStackRaster, ENVILayerStackRaster::Dehydrate, ENVIHydratable, ENVIHydrate