[Insight-users] itk::ConnectedComponentImageFilter ?

[Miller, James V (Research)]

The connected component image filter does not necessarily produce an 
image with contiguous labels.  All it guarentees is that the labels
are unique.  To collapse the components to be sequential requires 
an extra pass through the image. Since many consumers of connected 
components do not care if the labels are sequential, we do not make
this extra pass through the image.

You can run the output of the connected component image filter through
a RelabelComponentImageFilter which will renumber the components to
be sequential and sorted based on size.

Jim



-----Original Message-----
From: Lagaffe [mailto:lagaffe74130 at yahoo.fr]
Sent: Wednesday, January 12, 2005 7:38 AM
To: ITK mailing
Subject: [Insight-users] itk::ConnectedComponentImageFilter ?


Hello,
I don't understand why when I use the
ConnectedComponentImageFilter on the input image below
there is 4 labels instead of 3 ?
any idea 

thanks,
Lagaffe

The PixelType for the inputImage is  unsigned short

typedef itk::ConnectedComponentImageFilter <
ImageType, ImageType >
ConnectedComponentImageFilterType;
ConnectedComponentImageFilterType::Pointer labelFilter
= ConnectedComponentImageFilterType::New ();
   labelFilter->SetInput(inputImage);
   labelFilter->Update();

-  Input Image - -
0 0 0 0 0 1 1
0 0 0 0 0 0 1
0 0 0 0 0 0 0
0 0 1 0 0 0 0
0 1 1 1 0 0 0
0 0 1 0 0 0 0
0 0 0 0 1 1 1
0 0 0 0 0 1 1

- Label Image - -
0 0 0 0 0 1 1
0 0 0 0 0 0 1
0 0 0 0 0 0 0
0 0 2 0 0 0 0
0 2 2 2 0 0 0
0 0 2 0 0 0 0
0 0 0 0 4 4 4
0 0 0 0 0 4 4



	

	
		
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