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SplitRegionIntoBlobs

Header:	AVL.h
Namespace:	avl
Module:	FoundationBasic

Splits a region into an array of regions corresponding to its connected components.

Applications: Segmentation of a region into individual objects when the objects do not touch each other.

Syntax

void avl::SplitRegionIntoBlobs
(
	const avl::Region& inRegion,
	avl::RegionConnectivity::Type inConnectivity,
	const int inMinBlobArea,
	atl::Optional<int> inMaxBlobArea,
	bool inRemoveBoundaryBlobs,
	atl::Array<avl::Region>& outBlobs,
	atl::Array<int>& diagBlobAreas
)

Parameters

Name	Type	Range	Default	Description
inRegion	const Region&			Input region
inConnectivity	RegionConnectivity::Type			Type of connectivity used for the region foreground
inMinBlobArea	const int	0 -	1	Minimal area of a resulting blob
inMaxBlobArea	Optional<int>	0 -	NIL	Maximal area of a resulting blob
inRemoveBoundaryBlobs	bool		False	Flag indicating whether the blobs on border of the input region should be removed or not
outBlobs	Array<Region>&
diagBlobAreas	Array<int>&			Areas of extracted blobs

Description

The operation computes an array of connected regions corresponding to the connected components of the input region pixels. Each region in the resulting array will have dimensions equal to those of the input region.

Resulting array will contain only regions which have area in range defined by inputs: inMinBlobArea and inMaxBlobArea.

Images below shows neighbor of the gray pixel in different inConnectivity selection.


inConnectivity.FourDirections	inConnectivity.EightDirections

Hints

In most cases this function works without any parametrization. Just pass a single region to the inRegion input.
To reject small blobs, which are often caused by noise, increase inMinBlobArea.
To reject big blobs, which sometimes appear due to some background pattern, define inMaxBlobArea.
Set inRemoveBoundaryBlobs to ignore blobs of partially visible objects, touching the edges of the image.

Examples

The image below show an input 10x10 pixels region.

Images below shows result of SplitRegionIntoBlobs filter with different inConnectivity.


inConnectivity.FourDirections	inConnectivity.EightDirections

Images below shows result of SplitRegionIntoBlobs filter with different inRemoveBoundaryBlobs.


inRemoveBoundaryBlobs = True	inRemoveBoundaryBlobs = False

Remarks

When inRemoveBoundaryBlobs is set to True all filters near the region boundary will be removed. The region boundary is described by region frame.

This filter is mostly used in Blob Analysis Technique please refer to our Machine Vision Guide - Blob Analysis article.

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.