[Insight-users] How to get the boundary points of an image

[Susana]

Hello,

I'd like to make a filter that generates a signed distance from a contour 
without previous knoledge of which region is inside the contour, and which 
is outside, so in order to change the sign of the outer region, I want to 
take the external points of the image. For a 2D image, I've tried to do 
this:

  typename OutputImageType::SizeType size = 
output->GetLargestPossibleRegion().GetSize();
  typename OutputImageType::IndexType index;

  //Take all the border pixels on the first direction
  for ( unsigned long k = 0 ; k < size[0] ; k++ )
   {
    index[0] = k;
    index[1] = 0;
    m_ContornoExterno->Push( index );
    index[1] = size[1] - 1;
    m_ContornoExterno->Push( index );
   }

  //Take all the border pixels on the second direction
  for ( unsigned long k = 1 ; k < size[1]-1 ; k++ )
   {
    index[0] = 0;
    index[1] = k;
    m_ContornoExterno->Push( index );
    index[0] = size[0] - 1;
    m_ContornoExterno->Push( index );
   }

m_ContornoExterno behaves like a FIFO queue. The problem is that it would 
only work for 2D images, and I'd like to extend it to 3D (and preferably 
ND). I've looked for iterators, but I haven't found any that does exactly 
that; the closest is ImageBoundaryFacesCalculator. Could you give me some 
advice about what to do?

Thank you,

Susana

----- Original Message ----- 
From: "Luis Ibanez" <luis.ibanez at kitware.com>
To: <sumercav at ono.com>
Cc: <insight-users at itk.org>
Sent: Tuesday, April 04, 2006 3:28 PM
Subject: Re: [Insight-users] How to get the boundary points of an image


>
> Hi Susana,
>
> What you want is to get the physical coordinates of the image corners  ?
>
> Do you want to do this in 3D ? or ND?
>
> The ImaggeBoundaryFacesCalculator is a more sophisticated object,
> it actually decompose your image in pieces suitable for running 
> neighborhood iterators in them. It is probably too complicated for
> what you actually want to compute.
>
>  Please give us more details of what you want to do.
>
>
>     Regards,
>
>
>         Luis
>
>
>
> -----------------------
> sumercav at ono.com wrote:
>> Hello everybody,
>>
>> I'd like to get all the boundary points of an N-dimensional image. In the
>> software guide I've found the ImageBoundaryFacesCalculator, but it seems
>> that it also takes the points of the inside, and it's not clear to me how
>> to get just the boundary points without the others. How could I do that?
>> I need it to apply later a breadth-first search on the rest of the image.
>>
>> Thank you,
>>
>>
>> Susana
>>
>>
>> _______________________________________________
>> Insight-users mailing list
>> Insight-users at itk.org
>> http://www.itk.org/mailman/listinfo/insight-users
>>
>>
>
>
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