[Insight-users] Edge tracking?

[Zachary Pincus]

Hello,

I submitted a 2D 'marching squares' alogrithm to the Insight Journal  
a while ago. It produces itk::PolyLineParametricPath objects from an  
image -- one path per contour detected. So if you have a segmented  
image with values 0 and 255 (say), you could use this filter to  
extract paths corresponding to the image contour at 127.5.

The paths are calculated at sub-pixel precision, so the result isn't  
a list of pixels like the algorithm Luis suggested below, but it  
shouldn't be hard to get what you want (curve integral) out of a  
PolyLineParametricPath.

http://insight-journal.org/dspace/handle/1926/165

Let me know if you have any questions.

Zach



On Aug 28, 2006, at 9:29 AM, Luis Ibanez wrote:

>
> Hi Jordi,
>
> Unfortunately ITK doesn't have such a filter.
>
> It will be a very useful filter to have though.
>
>
> A typical algorithm for implementing this filter could be:
>
> 1) use a RegionIterator for going trhough the image until
>    a first pixel is found to be inside the segmentation.
>    Use that pixel as starting point for the path.
>
> 2) from that pixel start testing the neighbors clockwise,
>    and taking the first neighbor that is inside the segmented
>    object. Then push the currnt index into the itkPath, and
>    move to the neigbor just found.
>
>
> Such a filter would be a nice contribution to the Insight Journal.
>
> Please let us know if you are interested in implementing this
> filter. We will be happy to asist you in the process.
>
>
>   Thanks
>
>
>     Luis
>
>
>
> ---------------------
> Jordi Inglada wrote:
>> Hi all,
>> I have a region resulting from a segmentation and I would like to get
>> the list of the pixels which are located on the border of the  
>> segmented
>> region.
>> I need an ordered list, since I want to compute a curvilinear  
>> integral.
>>  I would like to know if there exists an ITK filter to get an  
>> itk::Path
>> or something similar from a detected edge.
>> Thank you for your help.
>> Jordi
>
>
> _______________________________________________
> Insight-users mailing list
> Insight-users at itk.org
> http://www.itk.org/mailman/listinfo/insight-users