[Insight-users] A few questions

[Feng Ma]

Hi,

  May I ask a few questions regarding efficiently using ITK data structures? 
I have been reading the software guide. But apparently I haven't got the 
essences of ITK data structures yet.

  1. GetRequestedRegion(), GetLagestPossibleRegion(), GetBufferedRegion(), 
which one to use? I have an itk image. I want to go through all the image 
voxels sequentially. I guess I should use itk::ImageRegionConstIterator to 
walk through the image. To construct this iterator, I need to provide a 
region. Which one should I use? Intuitively, I want to use 
GetLarestPossibleRegion() to make sure I will be able to visit every voxel. 
In many examples, we use GetRequestedRegion(). Does that gurantee me to 
visit every voxel in iimages?

  2. How to visit selected regions (random access voxels) efficiently? 
Suppose I have a region, through watershed or region growing. I recorded 
voxels in this region in a PointSet. After some processing, I need to visit 
the same region again. Suppose this is a relatively small region compared to 
the whole image. I don't want to visit the whole image and find this region 
again. It is better to be able to directly visit each voxels in the 
PointSet. The software guide said using SetPixel() is not efficient and 
"very slow". Which iterator shall I use to random access those voxels?

  3. Region growing: Is there a region growing filter which takes one or 
more seeds and grows from these seeds (with certain threshold values), and 
return a PointSet of grown region?

  4. Non-image-to-image filters? Seems that most filters are image to image 
filters. That means if I want to access resulted region, I need to scan the 
image and find the region I am interested in.

  Thanks a lot.

-Feng

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