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CheckPresence_EdgeAmount

Header:	AVL.h
Namespace:	avl
Module:	FoundationPro

Verifies object presence by analysing the amount of edges in the specified region.

Applications: Quick and easy presence verification, e.g. for missing caps, screws, labels.

Syntax

void avl::CheckPresence_EdgeAmount
(
	const avl::Image& inImage,
	const avl::ShapeRegion& inRoi,
	atl::Optional<const avl::CoordinateSystem2D&> inRoiAlignment,
	avl::GradientMaskOperator::Type inEdgeOperator,
	avl::MagnitudeMeasure::Type inEdgeMeasure,
	const int inEdgeScale,
	int inMinStrength,
	float inMinAmount,
	float inMaxAmount,
	bool& outIsPresent,
	atl::Optional<float&> outAmount = atl::NIL,
	atl::Optional<avl::Region&> outForeground = atl::NIL,
	atl::Optional<avl::ShapeRegion&> outAlignedRoi = atl::NIL
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Input image
inRoi	const ShapeRegion&			Location at which object presence is being checked
inRoiAlignment	Optional<const CoordinateSystem2D&>		NIL	Adjusts the region of interest to the position of the inspected object
inEdgeOperator	GradientMaskOperator::Type			Selected gradient operator
inEdgeMeasure	MagnitudeMeasure::Type		Sum	Selected method of gradient magnitude computation
inEdgeScale	const int	1 - 16	1	Scales the resulting gradient magnitudes
inMinStrength	int	0 - 255	15	Lowest acceptable edge magnitude
inMinAmount	float	0.0 - 1.0	0.2f	Lowest acceptable fraction of pixels meeting the criteria
inMaxAmount	float	0.0 - 1.0	1.0f	Highest acceptable fraction of pixels meeting the criteria
outIsPresent	bool&			Flag indicating whether the object is present or not
outAmount	Optional<float&>		NIL	Fraction of pixels from meeting the criteria
outForeground	Optional<Region&>		NIL	Region of pixels meeting the criteria
outAlignedRoi	Optional<ShapeRegion&>		NIL	Input ROI after transformation (in the image coordinates)

Optional Outputs

The computation of following outputs can be switched off by passing value atl::NIL to these parameters: outAmount, outForeground, outAlignedRoi.

Description

The filter extracts foreground pixels and checks if their number comparing to the area of the whole ROI fits the range (inMinAmount, inMaxAmount). The pixel is considered a foreground pixel if and only if its gradient magnitude is at least inMinStrength.

Hints

If the object location is variable, Pass an appropriate local coordinate system to inRoiAlignment.
Define inRoi to specify the image location at which the object presence will be checked.
Set inMinStrength to a value that results in good edges visible on the outForeground output.
Investigate the values that appear on the outAmount output, then set inMinAmount and inMaxAmount to values appropriate for correct objects.
When creating data previews, use outAlignedRoi and NOT inRoi as only the former will be properly aligned to the object location.

Examples

CheckPresence_EdgeAmount performed on sample images with inMinAmount = 0.2. In the left image the object is present, while in the right image it is not. Green pixels are foreground pixels.

Errors

List of possible exceptions:

Error type	Description
DomainError	Region exceeds an input image in CheckPresence_EdgeAmount.