[Insight-users] extrapolate filter

[Kevin H. Hobbs]

On Wed, 2009-08-19 at 11:07 -0700, Maarten Beek wrote:
> I have found the classes itkExtrapolateImageFunction and
> itkNearestNeighborExtrapolateImageFunction, however I am unable to
> find image filters that use this functionality. Does a filter like
> this exist?
> 
> I would like to "close" a bone fracture gap in a CT image.
> 
> Maarten


I do not think that extrapolation is what you are looking for.

Extrapolation implies that values will be assigned to positions outside
of the image.

For your task of closing a break in the image you might want to try the
GrayscaleMorphologicalClosingImageFilter here:

http://www.itk.org/Doxygen/html/classitk_1_1GrayscaleMorphologicalClosingImageFilter.html

or the binary equivalent here :

http://www.itk.org/Doxygen/html/classitk_1_1BinaryMorphologicalClosingImageFilter.html

They do a dilation of the image followed by an erosion of the image.

so if your image looks like this :

______________________
|                     |
|                     |
|                     |
|********** **********|
|                     |
|                     |
|_____________________|

then the dilation would look like this :

______________________
|                     |
|                     |
|*********************|
|*********************|
|*********************|
|                     |
|_____________________|


and then the erosion would look like this :
______________________
|                     |
|                     |
|                     |
|*********************|
|                     |
|                     |
|_____________________|

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