PixelPurityIndex Task

This task performs a pixel purity index (PPI) calculation on an input minimum noise fraction (MNF) result.

Example

This example runs a forward MNF transform on an area of disturbed earth in an AVIRIS hyperspectral image. It then creates a PPI image.

; Start the application

e = ENVI()

; Open an input file

File = Filepath('AVIRISReflectanceSubset.dat', $

  SUBDIR=['data','hyperspectral'], $

  ROOT_DIR=e.Root_Dir)

Raster = e.OpenRaster(File)

; Run a Forward MNF on the subset

mnfTask = EnviTask('ForwardMNFTransform')

mnfTask.INPUT_RASTER = Raster

mnfTask.Execute

; Run the PPI on the MNF result

ppiTask = ENVITask('PixelPurityIndex')

ppiTask.INPUT_RASTER = mnfTask.OUTPUT_RASTER

ppiTask.Execute

; Get the data collection

dataColl = e.Data

; Add the output to the data collection

dataColl.Add, ppiTask.OUTPUT_RASTER

; Display the result

View = e.GetView()

Layer = View.CreateLayer(ppiTask.OUTPUT_RASTER)

Syntax

Result = ENVITask('PixelPurityIndex')

Input parameters (Set, Get): INPUT_RASTER, ITERATIONS, OUTPUT_RASTER_URI, RESIZE_FACTOR, THRESHOLD

Output parameters (Get only): OUTPUT_HISTOGRAM, 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 the pixel purity index calculation.

ITERATIONS (optional)

Specify the number of iterations for the pixel purity index calculation. The default value is 1000.

OUTPUT_HISTOGRAM

Specify an array to receive the histogram of the pixel purity index result.

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.