LabelRegions Task

This task separates an image into regions, which are groups of contiguous pixels that share the same value. It consecutively labels all of the regions with a unique index. This task typically accepts classification images or binary masks as input.

The following diagram shows how distinct regions (with a pixel value of 1) are assigned different labels. The colors are meant for illustration only, to show the different labels assigned to each region.

Example

This example identifies water pixels in a multispectral image and labels each region separately. It uses a color slice classification to color the individual regions.

; 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)

; Create a spatial subset

SubsetTask = ENVITask('SubsetRaster')

SubsetTask.INPUT_RASTER = Raster

SubsetTask.SUB_RECT = [256,253,1023,941]

SubsetTask.Execute

; Get the water pixels

MathTask = ENVITask('PixelwiseBandMathRaster')

MathTask.INPUT_RASTER = SubsetTask.OUTPUT_RASTER

MathTask.EXPRESSION = 'b3 le 180'

MathTask.Execute

; Apply a binary morphological filter

FilterTask = ENVITask('BinaryMorphologicalFilter')

FilterTask.INPUT_RASTER = MathTask.OUTPUT_RASTER

FilterTask.METHOD = 'Open'

FilterTask.KERNEL = [[!true,!true,!true], $

  [!true,!true,!true], [!true,!true,!true]]

FilterTask.ITERATIONS = 1

FilterTask.Execute

; Label the regions

LabelTask = ENVITask('LabelRegions')

LabelTask.INPUT_RASTER = FilterTask.OUTPUT_RASTER

LabelTask.Execute

; Run color slice classification

ColorTask = ENVITask('ColorSliceClassification')

ColorTask.INPUT_RASTER = LabelTask.OUTPUT_RASTER

ColorTask.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, ColorTask.OUTPUT_RASTER

; Display the result

View = e.GetView()

Layer = View.CreateLayer(ColorTask.OUTPUT_RASTER)

Syntax

Result = ENVITask('LabelRegions')

Input parameters (Set, Get): INPUT_RASTER, 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 single-band raster.

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.