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

LOOKS (optional)

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

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.