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  >  Docs Center  >  ENVI API  >  Processing  >  ENVIAdditiveLeeAdaptiveFilterTask

ENVIAdditiveLeeAdaptiveFilterTask

ENVIAdditiveLeeAdaptiveFilterTask

This task applies a Lee adaptive filter to smooth noisy data that has an additive component.

Lee filtering is a standard deviation-based (sigma) filter that filters data based on statistics calculated within individual filter windows. Unlike a typical low-pass smoothing filter, the Lee filter and other similar sigma filters preserve image sharpness and detail while suppressing noise. The filtered pixel is replaced by a value calculated using the surrounding pixels.

Reference

Lee, Jong-Sen, “Digital Image Enhancement and Noise Filtering by Use of Local Statistics,” IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol PAMI-2, No.2, March 1980, pp. 165-168.

Example


; Start the application
e = ENVI()
 
; Open an input file
File = Filepath('qb_boulder_msi', Subdir=['data'], $
  Root_Dir=e.Root_Dir)
Raster = e.OpenRaster(File)
 
; Process a spatial subset
Subset = ENVISubsetRaster(Raster, Sub_Rect=[600,200,799,399])
 
; Get the task from the catalog of ENVITasks
Task = ENVITask('AdditiveLeeAdaptiveFilter')
 
; Define the task input raster
Task.INPUT_RASTER = Subset
 
; Define a size for the square (NxN) filtering window
Task.WINDOW_SIZE = 5
 
; Define a noise variance value
Task.NOISE_STANDARD_DEVIATION = 0.015
 
; Define the task output URI
Task.OUTPUT_RASTER_URI = e.GetTemporaryFilename()
 
; Run the task
Task.Execute
 
; Get the collection of data objects currently available in the Data Manager
DataColl = e.Data
 
; Add the output to the Data Manager
DataColl.Add, Task.Output_Raster
 
; Display the result
View = e.GetView()
Layer = View.CreateLayer(Task.Output_Raster)

Syntax


Result = ENVITask('AdditiveLeeAdaptiveFilter')

Input properties (Set, Get): INPUT_RASTER, NOISE_STANDARD_DEVIATION, OUTPUT_RASTER_URI, WINDOW_SIZE

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

This task also contains the following properties:

INPUT_RASTER (required)

Specify a raster on which to perform additive Lee adaptive filtering.

NOISE_STANDARD_DEVIATION (optional)

Specify the noise standard deviation. The default value is 0.25.

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 of the associated OUTPUT_RASTER. If you do not specify this property, or set it to an exclamation symbol (!), a temporary file will be created.

WINDOW_SIZE (optional)

Specify a square filtering window size, in pixels. The default value is 3.

Version History


ENVI 5.3

Introduced

API Version


3.2

See Also


ENVITask, ENVITask::Parameter, ENVISubsetRaster, ENVIAdditiveMultiplicativeLeeAdaptiveFilterTask, ENVIBitErrorAdaptiveFilterTask, ENVIEnhancedFrostAdaptiveFilterTask, ENVIEnhancedLeeAdaptiveFilterTask, ENVIFrostAdaptiveFilterTask, ENVIGammaAdaptiveFilterTask, ENVIKuanAdaptiveFilterTask, ENVILocalSigmaAdaptiveFilterTask, ENVIMultiplicativeLeeAdaptiveFilterTask



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