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CreateGrayModel

Header:	AVL.h
Namespace:	avl
Module:	MatchingBasic

Creates a model for NCC or SAD template matching.

Applications: Dynamic creation of models in the runtime environment (normally they are created interactively in Studio).

Syntax

void avl::CreateGrayModel
(
	const avl::Image& inImage,
	atl::Optional<const avl::Region&> inTemplateRegion,
	atl::Optional<const avl::Rectangle2D&> inReferenceFrame,
	int inMinPyramidLevel,
	atl::Optional<int> inMaxPyramidLevel,
	float inMinAngle,
	float inMaxAngle,
	float inAnglePrecision,
	float inMinScale,
	float inMaxScale,
	float inScalePrecision,
	avl::GrayModel& outGrayModel,
	atl::Optional<avl::Point2D&> outGrayModelPoint = atl::NIL,
	atl::Array<avl::Image>& diagTemplatePyramid
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Image from which model will be extracted
inTemplateRegion	Optional<const Region&>		NIL	Region of the image from which model will be extracted
inReferenceFrame	Optional<const Rectangle2D&>		NIL	Exact position of the model object in the image
inMinPyramidLevel	int	0 - 12	0	Defines the index of the lowest reduced resolution level used to speed up computations
inMaxPyramidLevel	Optional<int>	0 - 12	NIL	Defines the number of reduced resolution levels used to speed up computations
inMinAngle	float		0.0f	Start of range of possible rotations
inMaxAngle	float		0.0f	End of range of possible rotations
inAnglePrecision	float	0.001 - 10.0	1.0f	Defines angular resolution of the matching process
inMinScale	float	0.0 -	1.0f	Start of range of possible scales
inMaxScale	float	0.0 -	1.0f	End of range of possible scales
inScalePrecision	float	0.001 - 10.0	1.0f	Defines scale resolution of the matching process
outGrayModel	GrayModel&			Created model that can be used by LocateMultipleObjects_NCC and LocateMultipleObjects_SAD filters
outGrayModelPoint	Optional<Point2D&>		NIL	The middle point of the created model
diagTemplatePyramid	Array<Image>&			Visualization of the model at different resolution levels

Optional Outputs

The computation of following outputs can be switched off by passing value atl::NIL to these parameters: outGrayModelPoint.

Description

The operation creates a Gray Matching model for the object represented in inTemplateRegion region in inImage image. The resulting model can be matched against any image using the LocateMultipleObjects_NCC filter or the LocateMultipleObjects_SAD filter.

The model consists of a pyramid of iteratively downsampled images, the original image being the first of them. The inMaxPyramidLevel parameter determines how many additional images of the pyramid shall be computed. Greater inMaxPyramidLevel values can speed up matching process considerably, but it should be set so the image on the highest pyramid level is not too distorted.

The inMinAngle and inMaxAngle parameters describe possible rotation angles of the model, i.e. only those object occurrences will be later found by LocateMultipleObjects_NCC (or LocateMultipleObjects_SAD) whose rotation angles are in the range <inMinAngle,inMaxAngle>. The inAnglePrecision parameter controls the angular resolution of the matching process. The model is created in several rotations. The angles of consecutive rotations differ by an angle step from each other. The value of this angle step is determined on the basis of inAnglePrecision. Its value represents the multiplicity of the automatically computed angle step used as an actual step. So the greater inAnglePrecision is, the greater accuracy can be achieved and the lower is the chance of missing object occurrences. In practice however increasing inAnglePrecision above a certain threshold (unique for every object) does not increase the accuracy, only the computation time.

The inReferenceFrame is a characteristic rectangle, the position of which will be returned by LocateMultipleObjects_NCC (or LocateMultipleObjects_SAD) as an occurrence of the object. By default, it is set to the bounding box of the inTemplateRegion.

Remarks

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.

Additional information about Template Matching can be found in Machine Vision Guide: Template Matching

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.

Errors

List of possible exceptions:

Error type	Description
DomainError	Incorrect scale range in CreateGrayModel.
DomainError	Minimal pyramid level cannot be greater than maximal pyramid level in CreateGrayModel.
DomainError	Region of interest exceeds an input image in CreateGrayModel.