[Insight-users] Submission: FullyConnectedImageFilter to comp lement ConnectedComponentImageFilter

[Miller, James V (Research)]

For vertex+face connected, we may need to add another pixel to the shape
neighborhood, to be

    x  x  x
    x  x  .
    .  .  .

as opposed to the one I just posted

    x  x  .
    x  x  .
    .  .  .

-----Original Message-----
From: Miller, James V (Research) [mailto:millerjv at crd.ge.com]
Sent: Monday, February 16, 2004 8:48 AM
To: 'Zachary Pincus'; insight-users at itk.org
Subject: RE: [Insight-users] Submission: FullyConnectedImageFilter to
comp lement ConnectedComponentImageFilter


Zach, 

If the only real difference is checking vertex connected neighbors as well 
as face connected neighbors, couldn't the same code as
ConnectedComponentImageFilter
be used by "activating" a few more neighbors in the iterator?

In 2D, the ConnectedComponentImageFilter uses a neighborhood structure like

    .  x  .
    x  x  .
    .  .  .

with only the elements marked with "x" being activated.  If we put a mode
into the 
ConnectedConfidenceImageFilter to switch between face and face+vertex
connected 
neighbors, then we would toggle between an interator set up like above and
one
like

    x  x  .
    x  x  .
    .  .  .

Then the same algorithm code can be used, and the mode would just change the
setup code.

It looks like your version of the code actually checks the neighborhood

    x  x  x
    x  x  x
    x  x  x

which checks pixels in front of and behind the current pixel.  Isn't this
doing more work
than necessary?

Jim



-----Original Message-----
From: Zachary Pincus [mailto:zpincus at stanford.edu]
Sent: Sunday, February 15, 2004 11:10 PM
To: insight-users at itk.org
Subject: [Insight-users] Submission: FullyConnectedImageFilter to
complement ConnectedComponentImageFilter


Hello,

Here is an image filter that labels thin contours in binary images.

While ITK includes a ConnectedComponentImageFilter, this filter only 
works for face-connected objects (in 2-d, that's 4-connected), such as 
blobs. For single-pixel-thick contours, one needs to trace all the 
diagonal connections too (in 2-d, that's 8-connected), so this filter 
is not sufficient.

I have modified itkConnectedComponentImageFilter to trace contours 
across diagonals and faces in n dimensions. (It was a simple, but not 
totally trivial modification.) Here is my code, in case anyone needs 
it, or the ITK maintainers feel that it would be worth including in the 
repository.

(Note that I tried to integrate this into the original 
itkConnectedComponentImageFilter code to avoid excess code duplication, 
but that became really kludgy and unworkable due to the interface 
differences between ShapedNeighborhoodIterator::Iterator and 
Neighborhood::Iterator -- this is a bit of a pain, really.)

Also, in the future, what is the preferred method of code submission?

Zach Pincus

Department of Biochemistry and Program in Biomedical Informatics
Stanford University School of Medicine

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