BitErrorAdaptiveFilter Task

This task applies a bit error adaptive filter to a raster, to remove bit-error noise, which is usually the result of spikes in the data caused by isolated pixels that have extreme values unrelated to the image scene.

The noise typically gives the image a speckled appearance. Bit-error removal in ENVI uses an adaptive algorithm to replace spike pixels with the average of neighboring pixels. The local statistics (mean and standard deviation) within the filter box are used to set a threshold for valid pixels.

Reference

Eliason, Eric M. and McEwen, Alfred S., “Adaptive Box Filters for Removal of Random Noise from Digital Images,” Photogrammetric Engineering & Remote Sensing, April, 1990, V56 No. 4, p. 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('BitErrorAdaptiveFilter')

; Define an input raster

Task.INPUT_RASTER = Raster

; Specify true to replace bit errors with the

; local average. False sets bad pixels to zero.

Task.REPLACE_BIT_ERRORS = !true

; 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('BitErrorAdaptiveFilter')

Input properties (Set, Get): INPUT_RASTER, NOISE_STANDARD_DEVIATIONS, OUTPUT_RASTER_URI, REPLACE_BIT_ERRORS, TOLERANCE, VALID_MAXIMUM, VALID_MINIMUM, 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 bit error adaptive filtering.

NOISE_STANDARD_DEVIATIONS (optional)

Specify the noise standard deviation. The default value is 1.0.

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.

REPLACE_BIT_ERRORS (optional)

Specify true to replace bit errors with the local average. Specify false to set bad pixels to zero.

TOLERANCE (optional)

Specify the maximum standard deviation tolerance. The default value is 5.0.

VALID_MAXIMUM (optional)

Specify the maximum value for valid data.

VALID_MINIMUM (optional)

Specify the minimum value for valid data.

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