ENVITiePointSet::Offset

The Offset function method subtracts pixel offsets from all of the tie points in an ENVITiePointSet object. Use this method when applying tie points from a full input image to a spatially subsetted image.

Example

This example uses a sample auto-generated tie point file that was created by choosing the default options in the Image Registration workflow, using two input images quickbird_2.4m.dat and ikonos_4.0m.dat. The sample tie point file (SampleTiePoints.pts) and images are available from the ENVI Tutorials web page. Click the Image Registration link to download the .zip file to your machine, then unzip the files. Edit SampleTiePoints.pts to include the full path to the sample images quickbird_2.4m.dat and ikonos_4.0m.dat.

; Start the application

e = ENVI()

; Open an existing tie point file

tiePointFile = 'SampleTiePoints.pts'

tiePoints = ENVITiePointSet(tiePointFile)

; Subtract an offset

newPoints = tiePoints.Offset(2.0, 2.0, 2.0, 2.0)

; Create a new ENVITiePointSet object

newTiePoints = ENVITiePointSet(TIEPOINTS=newPoints, $

  INPUT_RASTER1=tiePoints.INPUT_RASTER1, $

  INPUT_RASTER2=tiePoints.INPUT_RASTER2)

Syntax

Result = ENVITiePointSet.Offset(Column1Offset, Row1Offset, Column2Offset, Row2Offset [, ERROR=variable])

Return Value

This method returns the subtracted pixel offsets from all of the tie points in an ENVITiePointSet object.

Arguments

Column1Offset

Specify the column offset (in pixels) in the first input image. The new Column1 coordinate will be the original Column1 value minus Column1Offset.

Row1Offset

Specify the row offset (in pixels) in the first input image. The new Row1 coordinate will be the original Row1 value minus Row1 offset.

Column2Offset

Specify the column offset (in pixels) in the second input image.

Row2Offset

Specify the row offset (in pixels) in the second input image.

Keywords

ERROR (optional)

Set this keyword to a named variable that will contain any error message issued during execution of this routine. If no error occurs, the ERROR variable will be set to a null string (''). If an error occurs and the routine is a function, then the function result will be undefined.

When this keyword is not set and an error occurs, ENVI returns to the caller and execution halts. In this case, the error message is contained within !ERROR_STATE and can be caught using IDL's CATCH routine. See IDL Help for more information on !ERROR_STATE and CATCH.

See Manage Errors for more information on error handling in ENVI programming.

Version History

ENVI 5.2. 1

Introduced

API Version

4.2