[Insight-users] Where is the Polygon Scan Converter?

[Miller, James V (Research)]

Frank,

The polygon scan converter code needed some work before it could be
incorporated into the toolkit. I tried to do it quickly before the 
last release but couldn't finish it in time.  It currently crashes
when I try to use it.  

I will try to get this operational and included in the toolkit for
the next release which is scheduled for the end of November.

A brute force way to do what you want is to construct a PolygonSpatialObject
and use a SpatialObjectToImageFilter to generate the initial implicit
function.  This is not very efficient when polygon is small relative 
to the size of image, but it will do what you need.

Jim



-----Original Message-----
From: insight-users-bounces+millerjv=crd.ge.com at itk.org
[mailto:insight-users-bounces+millerjv=crd.ge.com at itk.org]On Behalf Of
Frank Miller
Sent: Friday, October 21, 2005 10:16 AM
To: insight-users at itk.org
Subject: [Insight-users] Where is the Polygon Scan Converter?


Greetings,

Im using level set methods to work on a segmentation problem and wrote a 
little function that I think this community would be interested in.

Problem
-------

The standard way to generate an initial implicit function is to create a 
distance map from a set of seed points using the FastMarchingImageFilter 
or the DanielssonDistanceMapImageFilter. It would be nice to be able to 
generate the initial implicit function given a level set. In other 
words, to have a method to generate an implicit function that has an 
arbitrary polygon for its zero level set.

Solution
--------

I would expect many people would want to implement something like this 
and it is possible the solution is already in ITK and I just have not 
found it.  If this is the case, please point me in the right direction.

My solution is to create an image with zeros everywhere outside the 
polygon, and non-zeros inside the polygon, and feed this to the 
SignedDanielssonDistanceMapImageFilter.  I generate this binary image 
from a polygon scan conversion iterator written by Benjamin King and 
submitted in this post.

http://public.kitware.com/pipermail/insight-users/2005-June/013614.html

Questions
---------

The code for the polygon scan conversion iterator does not seem to be in 
the library (I checked the 2.0.0 release and the current version in 
CVS).  Has the name been changed or has it not been integrated yet?

Does someone need to volunteer to add this code to the library?  I might 
be able to do this.

Frank
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