LocalSigmaAdaptiveFilter Task

This task applies a Local Sigma adaptive filter to a raster, to preserve fine detail (even in low contrast areas) and to reduce speckle significantly.

The Local Sigma filter uses the local standard deviation computed for the filter box to determine valid pixels within the filter window. It replaces the pixel being filtered with the mean calculated using only the valid pixels within the filter box.

Reference: Eliason, E. and A. McEwen. "Adaptive Box Filters for Removal of Random Noise from Digital Images." Photogrammetric Engineering & Remote Sensing 56, No. 4 (1990): 453.

Example

; Start the application

e = ENVI()

; Open an input file

File = Filepath('elev_t.jpg', Subdir=['examples','data'])

Raster = e.OpenRaster(File)

; Get the task from the catalog of ENVITasks

Task = ENVITask('LocalSigmaAdaptiveFilter')

; Define inputs

Task.INPUT_RASTER = Raster

; 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('LocalSigmaAdaptiveFilter')

Input properties (Set, Get): INPUT_RASTER, NOISE_STANDARD_DEVIATIONS, 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 Local Sigma adaptive filtering.

NOISE_STANDARD_DEVIATIONS (optional)

Specify the number of standard deviations used to determine valid pixels within the filter window. The default value is 1.0. ENVI determines which pixels are valid by calculating a minimum and maximum pixel value based on the number of standard deviations and the local statistics. It replaces the pixel being filtered with the mean calculated using only the valid pixels within the filter box.

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