AdditiveLeeAdaptiveFilter Task

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 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:

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

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

4.2