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 parameters (Set, Get): INPUT_RASTER, MEAN, OUTPUT_RASTER_URI

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 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_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.