ImageBandDifference Task

This task performs a difference analysis on a specific band in two images.

Example

This example performs a difference analysis between two images from different dates. The images represent NCEP-Reanalysis 2 air temperatures (K) at the 1000-isobar level, at 0600 hours Zulu time. The first image is from 29 December 2012, and the second is from 31 December 2012. Each image has one band. This example uses sample data from the ENVI installation path.

; Start the application

e = ENVI()

TimeSeriesDir = Filepath('', Subdir=['data','time_series'], $

  Root_Dir = e.Root_Dir)

files = File_Search(TimeSeriesDir, 'AirTemp*.dat')

numRasters = N_Elements(files)

rasters = ObjArr(numRasters)

FOR i=0, (numRasters-1) DO $

  rasters[i] = e.OpenRaster(files[i])

; Get the task from the catalog of ENVITasks

Task = ENVITask('BuildTimeSeries')

; Define inputs

Task.INPUT_RASTERS = rasters

; Run the task

Task.Execute

; Get the raster that corresponds to 0600, 29 December 2012 (index #1)

; Indices are zero-based.

SeriesFile = Task.OUTPUT_RASTERSERIES

SeriesFile.Set, 0

Image1 = SeriesFile.Raster

; Get the raster that corresponds to 0600, 31 December 2012 (index #9)

; Indices are zero-based.

SeriesFile.Set, 8

Image2 = SeriesFile.Raster

; Get the task from the catalog of ENVITasks

Task = ENVITask('ImageBandDifference')

; Define inputs

Task.INPUT_RASTER1 = Image1

Task.INPUT_RASTER2 = Image2

; 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('ImageBandDifference')

Input parameters (Set, Get): INPUT_RASTER1, INPUT_RASTER2, 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_RASTER1 (required)

Specify the first raster on which to perform the image band difference.

INPUT_RASTER2 (required)

Specify the second raster on which to perform the image band difference. It must have the same number of columns, rows, and bands as INPUT_RASTER1.

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.

Output Parameters

OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI. It inherits the same map information (projection, datum, pixel size, image rotation) and wavelengths as INPUT_RASTER1.