FlatFieldCorrection Task

This task performs Flat Field correction to normalize images to an area of known flat reflectance. This is particularly effective for reducing hyperspectral data to relative reflectance.The average spectrum from a region of interest (ROI) can be used as the reference spectrum, which is then divided into the spectrum for each pixel of the image.

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)

; Open ROIs

fileName = Filepath('qb_boulder_roi.xml', SUBDIR=['data'], $

ROOT_DIR=e.Root_Dir)

rois = e.OpenRoi(fileName)

; Calculate ROI statistics

TaskStats = ENVITask('ROIStatistics')

TaskStats.INPUT_RASTER = Raster

; Specify the ROI for Water. We assume that water pixels

; have flat spectra.

TaskStats.INPUT_ROI = rois[2]

; Run the task

TaskStats.Execute

; Get the task from the catalog of ENVITasks

Task = ENVITask('FlatFieldCorrection')

; Define inputs

Task.INPUT_RASTER = Raster

Task.MEAN = TaskStats.MEAN

; 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('FlatFieldCorrection')

Input properties (Set, Get): INPUT_RASTER, MEAN, OUTPUT_RASTER_URI

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 flat field correction.

MEAN (required)

Specify an array of floating-point values to divide into each band. The array size must be equal to the number of bands in the raster. To perform proper Flat Field correction, these mean values should be computed from a set of pixels of known flat spectral response.

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.

Version History

ENVI 5.5. 1

Introduced

API Version

4.2