This task performs the Constrained Energy Minimization (CEM) target analysis.
Example
This example performs the following steps:
-
Opens an AVIRIS hyperspectral image subset.
-
Runs a forward minimum noise transform (MNF) to reduce noise in the data.
-
Defines three regions of interest (ROIs), each containing nine pixels of a common material.
-
Retrieves the spectra from the ROIs and uses their means as targets for Constrained Energy Minimization.
-
Runs the CEM task, which performs constrained energy minimization target analysis.
-
Displays the result. To see all of the bands, open the Data Manager.
e = ENVI()
File = Filepath('AVIRISReflectanceSubset.dat', $
SUBDIR=['data', 'hyperspectral'], $
ROOT_DIR=e.Root_Dir)
Raster = e.OpenRaster(File)
Task = ENVITask('ForwardMNFTransform')
Task.INPUT_RASTER = Raster
Task.Execute
Subset = ENVISubsetRaster(Task.OUTPUT_RASTER, BANDS=LINDGEN(25))
nSpectra = 9d
roi1 = ENVIROI(NAME='Green Field')
pixelAddr1 = [[77,182],[78,182],[79,182], $
[77,183],[78,183],[79,183], $
[77,184],[78,184],[79,184]]
roi1.AddPixels, pixelAddr1, SPATIALREF=Subset.SPATIALREF
roi2 = ENVIROI(NAME='Soil')
pixelAddr2 = [[386,285],[387,285],[388,285], $
[386,286],[387,286],[388,286], $
[386,287],[387,287],[388,287]]
roi2.AddPixels, pixelAddr2, SPATIALREF=Subset.SPATIALREF
roi3 = ENVIROI(NAME='Ground')
pixelAddr3 = [[296,326],[297,326],[298,326], $
[296,327],[297,327],[298,327], $
[296,328],[297,328],[298,328]]
roi3.AddPixels, pixelAddr3, SPATIALREF=Subset.SPATIALREF
spectra1 = Subset.GetData(ROI=roi1)
mean1 = Total(spectra1,1) / nSpectra
spectra2 = Subset.Getdata(ROI=roi2)
mean2 = Total(spectra2,1) / nSpectra
spectra3 = Subset.GetData(ROI=roi3)
mean3 = Total(spectra3,1) / nSpectra
targets = [[mean1],[mean2],[mean3]]
Task = ENVITask('ConstrainedEnergyMinimization')
Task.INPUT_RASTER = Subset
Task.TARGET = targets
Task.Execute
dataColl = e.Data
dataColl.Add, Task.OUTPUT_RASTER
View = e.GetView()
Layer = View.CreateLayer(Task.OUTPUT_RASTER)
Syntax
Result = ENVITask('ConstrainedEnergyMinimization')
Input properties (Set, Get): BACKGROUND_THRESHOLD, COVARIANCE, INPUT_RASTER, NAMES, OUTPUT_RASTER_URI, TARGET, USE_COVARIANCE, USE_SUBSPACE_BACKGROUND
Output properties (Get only): OUTPUT_RASTER
Properties marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.
Methods
This task inherits the following methods from ENVITask:
AddParameter
Execute
Parameter
ParameterNames
RemoveParameter
Properties
This task inherits the following properties from ENVITask:
COMMUTE_ON_DOWNSAMPLE
COMMUTE_ON_SUBSET
DESCRIPTION
DISPLAY_NAME
NAME
REVISION
TAGS
This task also contains the following properties:
BACKGROUND_THRESHOLD (optional)
This is a float value indicating the fraction of the background in the anomalous image to use when calculating statistics using subspace background. It ranges from 0.500 to 1.000 (the entire image), with the default 0.9.
COVARIANCE (optional)
Specify an array that is the covariance matrix of the input bands. The array size must be [number of bands, number of bands].
INPUT_RASTER (required)
Specify an input raster to process.
NAMES (optional)
Specify an array of endmember names. The array size must be [number of endmembers].
OUTPUT_RASTER
This is a reference to the output raster of filetype ENVI.
OUTPUT_RASTER_URI (optional)
Specify a string with the fully qualified filename and path to export the associated OUTPUT_RASTER.
- If you set this property to an asterisk symbol (*), the output raster will be virtual and not written to disk.
- If you do not specify this property, or set it to an exclamation symbol (!), a temporary file will be created.
TARGET (required)
Specify the target spectra. It is a floating-point array. The array size is [number of bands, number of target spectra].
USE_COVARIANCE (optional)
Specify using the covariance matrix as background statistics instead of the input bands correlation matrix.
USE_SUBSPACE_BACKGROUND (optional)
Specify whether to use subspace background in statistics calculation.
Version History
ENVI 6.0 |
Introduced |
ENVI 6.1 |
Added the NAMES keyword.
|
API Version
4.3
See Also
ENVITask