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Harris Geospatial / Docs Center / ENVI API / Processing / ENVIFrostAdaptiveFilterTask

ENVIFrostAdaptiveFilterTask

ENVIFrostAdaptiveFilterTask

This task applies a Frost filter to a raster, to reduce speckling while preserving edges.

The Frost filter is an exponentially damped circularly symmetric filter that uses local statistics. The pixel being filtered is replaced with a value calculated based on the distance from the filter center, the damping factor, and the local variance.

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

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)
 
; Process a spatial subset
Subset = ENVISubsetRaster(Raster, Sub_Rect=[600,200,799,399])
 
; Get the task from the catalog of ENVITasks
Task = ENVITask('FrostAdaptiveFilter')
 
; Define the input raster
Task.INPUT_RASTER = Subset
 
; Define the damping factor
Task.DAMPING_FACTOR = 1.0
 
; Define output raster URI
Task.OUTPUT_RASTER_URI = e.GetTemporaryFilename()
 
; 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
View1 = e.GetView()
Layer1 = View1.CreateLayer(Task.Output_Raster)

Syntax


Result = ENVITask('FrostAdaptiveFilter')

Input properties (Set, Get): DAMPING_FACTOR, IGNORE_VALIDATE, INPUT_RASTER, OUTPUT_RASTER_URI, WINDOW_SIZE

Output properties (Get only): DESCRIPTION, NAME, 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:

AddParameter

Execute

Parameter

ParameterNames

RemoveParameter

Properties


DAMPING_FACTOR (optional)

Specify a floating-point damping factor that determines the amount of exponential damping. A value of 1.0 (the default) is sufficient for most radar images. Larger damping values preserve edges better but smooth less. A damping value of 0 results in the same output as a low pass filter.

DESCRIPTION

This property describes the task.

IGNORE_VALIDATE (optional)

This property is now deprecated and has no effect on task behavior. All task property values are validated when they are set, and they throw an error with bad input.

INPUT_RASTER (required)

Specify a raster on which to perform Frost adaptive filtering.

NAME

This property contains the name of the task.

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 output raster. If you do not specify this property, the output raster is only temporary. Once the raster has no remaining references, ENVI deletes the temporary file.

WINDOW_SIZE (optional)

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

Version History


ENVI 5.3

Introduced

API Version


3.1.0

See Also


ENVITask, ENVITask::Parameter, ENVISubsetRaster, ENVIAdditiveLeeAdaptiveFilterTask, ENVIAdditiveMultiplicativeLeeAdaptiveFilterTask, ENVIBitErrorAdaptiveFilterTask, ENVIEnhancedFrostAdaptiveFilterTask, ENVIEnhancedLeeAdaptiveFilterTask, ENVIGammaAdaptiveFilterTask, ENVIKuanAdaptiveFilterTask, ENVILocalSigmaAdaptiveFilterTask, ENVIMultiplicativeLeeAdaptiveFilterTask



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