[Insight-users] contours extraction

Luis Ibanez luis.ibanez at kitware.com
Wed Jun 16 15:08:44 EDT 2004

Hi Yann,

The processing that you are attempting to implement
is completely dependend on the discret topology
that you define for your pixels.

The first thing that you want to avoid is to use
4-connectedness and 8-connectedness since both
of them are flawed digital topologies, and for
your application it will be hopeless to attempt
a correct definition of what a "node" means.

The more consistent way of managing connections
in a discrete space in 2D is to use a 6-connected
topology.  In that context you could use the typical
engineering approach of considering connections
along the vertical and horizontal axis, and along
*only one* of the diagonals. In this way you get a
6-connected space where the notions of neighbors
can be properly defined.

You may want to look at the classical literature
on this area:

A. Rosenfeld, A. Kak
Digital picture processing
Academic Press Inc. 1982.

J. Serra
Image Analysis and Mathematical Morphology
Academic Press Inc. 1982
(You will notice that most of the "formal"
Mathematical Morphology is actually done in
hexadecimal grids)

D. Nogly, M. Schladt
Digital Topology on Graphs
Computer Vision and Image Understanding,
Vol 63, No.2; March; pp 394-396, 1996.

Your description was a bit confusing regarding
what you already have solved and what you are
looking for.

It seems that you already have succed to detect
the regions separating the cells, and now your
are trying to identify the cells themselves.

It is not clear why you need to identify the
nodes in the contours and why you plan still
to remove borders that are "not well detected".

Maybe a description of your "real final" goal
(not the intermediate difficulties) will be
useful for suggesting you appropriate ways
of taking advantage of the algorithms available
in ITK.

   Please let us know,



Yann GAVET wrote:

> Hi all.
> I want to perform a contour extraction from cell images.
> My program computes the skeleton of the contours, and I want to get the 
> cells (with itkConnectedComponentImagefilter).
> I also want to get the borders of the cells in a specific way, so that I 
> could remove easily the borders that are not well detected. The 
> important thing should be the detection of the "node" points, in red in 
> the picture. Then, I could separate the borders of the cells into 
> segments and manage segments easily.
> My question is: is there a way in itk to perform such a segmentation ? 
> Does anyone know any method or link that could help me ?
> Thank you for your time.
> Yann
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