AUTOREG

Description

The automatic registration function, given a reference image and a second input image (target image), applies a filtering and correlation process to determine the best affine transformation for registering the input image to the reference image.

Parameters

autoreg(fili_ref, dbic_ref, fili_ima, dbic_ima, filo, wchunks, cg_xoff, cg_yoff, patch, search, pfa, isonofac)

Name	Type	Caption	Length	Value range
FILI_REF *	str	Input reference image file	1 -
DBIC_REF	List[int]	Input reference channel	0 - 1	Default: 1
FILI_IMA *	str	Input image file	1 -
DBIC_IMA	List[int]	Input image channel	0 - 1	Default: 1
FILO *	str	Output file name	1 -
WCHUNKS	List[int]	Whitening chunk size	0 - 1	8 - 32 Default: 32
CG_XOFF	List[int]	Correlation grid X offset	0 - 1	32 - Default: 128
CG_YOFF	List[int]	Correlation grid Y offset	0 - 1	32 - Default: 128
PATCH	List[int]	Correlation patch size	0 - 1	0 - Default: 16
SEARCH	List[int]	Correlation search window	0 - 1	0 - Default: 32
PFA	List[float]	Probability of false alarm	0 - 1	0 - Default: 0.10
ISONOFAC	List[float]	Isolated noise factor	0 - 1	0 - Default: 0.10

* Required parameter

Parameter descriptions

FILI_REF

Specifies the input reference image file to which the input image file will be registered.

DBIC_REF

Specifies the image channel that contains the reference image.

Note: If AUTOREG is used in conjunction with an EASI script, this parameter can be reassigned to specify the correct working image channel being used.

FILI_IMA

Specifies the input image file to be registered to the reference image.

DBIC_IMA

Specifies the image channel that contains the image to be registered.

Note: If AUTOREG is used in conjunction with an EASI script, this parameter can be reassigned to specify the correct working image channel being used.

FILO

Specifies the output image file to receive the registered image output.

WCHUNKS

Specifies the size of the chunk of data used to whiten (edge enhance) the reference image and the image to be registered. This value must be a power of 2, and 32 or less. Normally a value 32 is best. A value of 16 will increase processing speed, but at the cost of accuracy.

CG_XOFF

Specifies the correlation grid X offset. This offset is used to ensure that no edge effects are included in the whitening or correlation of the data. The correlation grid X offset must be greater than or equal to half of the search size.

CG_YOFF

Specifies the correlation grid Y offset. This offset is used to ensure that no edge effects are included in the whitening or the correlation of the data. The correlation grid Y offset must be greater than or equal to half of the search size.

PATCH

Specifies the correlation patch size, that is, the size of the image chip for cross-correlation.

SEARCH

Specifies extent of the correlation search range which is the expected mis-registration. The search size must be greater than or equal to the correlation patch size.

PFA

Specifies the probability of false alarm. Decreasing this parameter removes control points that are not likely to be due to image structure.

ISONOFAC

Specifies the isolated noise factor. This parameter is not normally set by the user.

Return Value

Returns:

Type: PCI_INT

Returns the newly created GCP segment number. It the return is empty, no new segment is created.

Details

To correctly set the parameters for AUTOREG, follow these guidelines to get a good initial estimate of the parameter values:

Select a patch size between 16 and 32.
Specify a search window size >= patch size.
Make the correlation grid X and Y offsets >= 1/2 search window size > 32; also make the correlation grid X and Y offsets equal for square images.
Set the probability of false alarm (PFA) equal to 0.10.
Lower the PFA value for a better correlation, or increase the value for a looser correlation.

Example

Register channel 2 with channel 1 as the reference image. Place the output GCP points into a new GCP segment on the output file (FILO). Set the PATCH to 16 and then set the SEARCH to 32. Use a correlation grid offset of 128 pixels in the X and Y dimensions (CG_XOFF and CG_YOFF). The probability of false alarm (PFA) and the isolation noise factor (ISONOFAC) are both set to 0.1 and 32 whitening chunks (WCHUNKS) are chosen.

from pci.autoreg import autoreg

fili_ref	=	"pan_2000.pix"
dbic_ref	=	[1]
fili_ima	=	"pan_2000.pix"
dbic_ima	=	[2]
filo	=	"pan_2000.pix"
wchunks	=	[32]
cg_xoff	=	[128]
cg_yoff	=	[128]
patch	=	[16]
search	=	[32]
pfa	=	[0.1]
isonofac	=	[0.1]

autoreg( fili_ref, dbic_ref, fili_ima, dbic_ima, \
filo, wchunks, cg_xoff, cg_yoff, patch, \
search, pfa, isonofac )

Environments	PYTHON :: EASI :: MODELER
Quick links	Description :: Parameters :: Parameter descriptions :: Return Value :: Details :: Example