[Insight-users] Mask+Neumann Boundary Condition

[Brady McCary]

Luis,

A high-level description is:

1. Imagine an image with circular ROI.
2. Iterate a neighborhood over the ROI.
3. Use a BC when the neighborhood extends outside of the ROI.

Said with more details:

1. Input images are rectangular.
2. I want to be able to set a ROI and perform a computation only over
this ROI. The ROI will in general be non-rectangular.
3. This computation requires a neighborhood for each pixel in the ROI.
4. Some pixels in the ROI will be on the boundary of the ROI and
therefor the neighborhood will extend outside of the ROI.
5. In the case where pixels in the neighborhood are outside of the
ROI, I want to be able to use a boundary condition to compute their
values.
6. A Neumann-like BC will be fine.
7. Note that the usual grid-aligned, rectangular region is a convex
case (see next note).
8. Note that defining the Neumann BC for a non-convex region is more
complicated that the convex case.

I hope this clarifies my post. Please let me know if you need more information.

Brady

On Sun, Nov 8, 2009 at 1:20 PM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> Hi Brady,
>
> There are two mentions of a "Mask" in your email,
> and I'm wondering if we are interpreting them correctly.
>
> You say that you want an iterators that uses a
>
>                   "non-rectangular mask"
>
> do you mean that you want the iterator to visit all
> the pixels of a non-rectangular region of the image ?
>
> You are probably aware of the difference between the
> ITK ImageRegion iterators and the ITK Neighborhood
> Iterators.
>
> The use of Boundary conditions is relevant for the
> Neighborhood iterators, not for the RegionIterators.
>
> Could you please clarify if you are looking for
> a Neighborhood iterator or not ?
>
> and whether you need to look at the neighbors of
> every pixel in a particular pattern ?
>
> Maybe a high level description of what you are trying
> to achieve, will be very helpful here.
>
>
>      Thanks
>
>
>           Luis
>
>
> ----------------------------------------------------------------------------------------------------------
> On Tue, Nov 3, 2009 at 4:15 PM, Brady McCary <brady.mccary+ITK at gmail.com> wrote:
>> insight-users,
>>
>> Is there an neighborhood iterator which will use a non-rectangular
>> mask and a Neumann boundary condition? I.e., I would like an iterator
>> that will
>>
>> 1. Only iterate over a mask I supply (e.g., an itk::ImageMaskSpatialObject).
>> 2. Use the Neumann boundary condition to compute a neighborhood, using
>> information only within the mask.
>>
>> Brady
>> _____________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Kitware offers ITK Training Courses, for more information visit:
>> http://www.kitware.com/products/protraining.html
>>
>> Please keep messages on-topic and check the ITK FAQ at:
>> http://www.itk.org/Wiki/ITK_FAQ
>>
>> Follow this link to subscribe/unsubscribe:
>> http://www.itk.org/mailman/listinfo/insight-users
>>
>