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)
 
; Get the task from the catalog of ENVITasks
Task = ENVITask('AdditiveLeeAdaptiveFilter')
 
; Define the task input raster
Task.INPUT_RASTER = Raster
 
; Define a size for the square (NxN) filtering window
Task.WINDOW_SIZE = 5
 
; Define a noise variance value
Task.NOISE_STANDARD_DEVIATION = 0.015
 
; 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 parameters (Set, Get): INPUT_RASTER, NOISE_STANDARD_DEVIATION, OUTPUT_RASTER_URI, WINDOW_SIZE

Output parameters (Get only): OUTPUT_RASTER

Parameters marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Parameters marked as "Get" are those whose values you can retrieve but not set.

Input Parameters


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_URI (optional)

Specify a string with the fully qualified filename and path of the associated OUTPUT_RASTER.

  • If you do not specify this parameter, or set it to an exclamation symbol (!), ENVI creates a temporary file.
  • If you set it to the hash symbol (#), ENVI creates a file in the temporary directory, but this file will not be deleted when ENVI closes.

WINDOW_SIZE (optional)

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

Output Parameters


OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI.

Methods


Execute

Parameter

ParameterNames

Properties


DESCRIPTION

DISPLAY_NAME

NAME

REVISION

TAGS

Version History


ENVI 5.3

Introduced

See Also


ENVITask, ENVISubsetRaster, AdditiveMultiplicativeLeeAdaptiveFilter Task, BitErrorAdaptiveFilter Task, EnhancedFrostAdaptiveFilter Task, EnhancedLeeAdaptiveFilter Task, FrostAdaptiveFilter Task, GammaAdaptiveFilter Task, KuanAdaptiveFilter Task, LocalSigmaAdaptiveFilter Task, MultiplicativeLeeAdaptiveFilter Task, Masking Support in ENVITasks