[Insight-users] Newbie question: How to create polygons?

[Jazz Kartell]

Hi Luis,

thanks for your fast answer. I will play around with your suggestions...
i try to specify my problem:

e.g. i have a .png with a black filled circle... (for the beginning...)
Now ITK should find that black region (with treshold) and save it internal
as a polygon with n vertices. and that "internal" region i want to extract.
So for example with the circle:
I define n=4 and ITK should create the smallest square (or polygon with 
n edges) containing the whole circle...
The goal is that it is possible to define how exact a requested region 
is encircled.

Exporting that encircled region:
at this point, it would be nice to generate a seperate .png only 
containing the extracted polygon including the "circle"
or to encircle the region in the .png itself. But I think that should be 
not so hard to do, once the regions are accessible...

I hope now my problem is a bit clearer and sorry for my english ;-)

Thanks

Benjamin



Luis Ibanez schrieb:
>
> Hi Benjamin,
>
>
>               Welcome to ITK !
>
>
> You can extract contours from a binary image (your .png file)
> by using the filter:
> http://www.itk.org/Insight/Doxygen/html/classitk_1_1ContourExtractor2DImageFilter.html 
>
>
> ---
>
> However, from the description of your email, there seems to be
> a confusion between your goals and your means:
>
> Is it your final purpose:
>
>  A) To extract the individual shapes into separate image files ?
>
> or is it
>
>  B) To identify the polygonal representation of the shapes in
>     the input image ?
>
>
> If your goal is (A), then what you need is simply a pipeline
> with the following filters:
>
>     * ConnectedComponents
>     * BinaryThreshold
>     * RegionOfInterest
>
> If you goal is (B), then, you can use the ContourExtractor2D described
> above and then you can use Fourier descriptors in order to identify
> polygonal shapes in the output of this filter.
>
>
> Please separate your real goal from the means that you have
> planned to use, so that we can better advise you on what ITK
> components to use.
>
>
>
>       Thanks
>
>
>           Luis
>
>
>
> --------------------
> Jazz Kartell wrote:
>> Hi to everyone,
>>
>> I'm completely new to ITK, so please be lenient toward me...
>> At the moment i'm very overhelmed with all the functionality included 
>> in ITK.
>>
>> So here is what i want to do:
>>
>> Input is a simple .png file including black filled forms on white 
>> background.
>> Goal is to extract these forms in seperate files (one for each form).
>> The extracted region should be included in a polygon with predefined 
>> amount of vertices.
>>
>> Could you give me an advice, how i can enclose regions in polygons?
>>
>> Thank you very much in advance
>>
>> Best regards
>>
>> Benjamin Kirchholtes
>>
>>
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