GammaAdaptiveFilter Task

This task applies a gamma filter to a raster, to reduce speckle while preserving edges in radar images. Filtered pixels are replaced with values calculated from local statistics.

Reference: Zhenghao Shi, and Ko B. Fung. "A Comparison of Digital Speckle Filters." Proceedings of IGRASS 94, August 8-12, 1994, pp. 2129-2133.

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('GammaAdaptiveFilter')

; Define an input raster

Task.INPUT_RASTER = Raster

; Define task inputs

Task.LOOKS = 1

; 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('GammaAdaptiveFilter')

Input properties (Set, Get): INPUT_RASTER, LOOKS, 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 gamma adaptive filtering.

LOOKS (optional)

Specify the effective number of looks. The default value is 1. This property is used to calculate the noise variance by 1/(number of looks).

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. The default value is 3.

Version History

ENVI 5.3

Introduced

API Version

4.3