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 properties (Set, Get): INPUT_RASTER, ITERATIONS, OUTPUT_RASTER_URI, RESIZE_FACTOR, THRESHOLD
Output properties (Get only): OUTPUT_HISTOGRAM, 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:
This task also contains the following properties:
INPUT_RASTER (required)
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
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.
RESIZE_FACTOR (optional)
Specify a resize factor to subsample the input raster so that the entire file will fit into memory. The default value is 1.0.
THRESHOLD (optional)
Specify the threshold factor in data units for pure pixel selection. The default value is 2.5.
Version History
|
ENVI 5.5 |
Introduced |
API Version
4.2