[Insight-users] Finding out when a neighborhood iterator is o utside the image?

[Miller, James V (Research)]

Here is my current thoughts.

NeighborhoodIterator has a method 

SetPixel(const unsigned i, const PixelType &v, bool& status) 

where the "status" is set to true if the pixel was set and false
if the location i is outside the image.

So am I adding a version of 

GetPixel(const unsigned i, bool& IsInBounds)

to ConstNeighborhoodIterator which sets the boolean IsInBounds
as to whether the pixel value returned is an actual pixel or a 
boundary condition value.

How does that sound?

Jim



-----Original Message-----
From: Joshua Cates [mailto:cates at sci.utah.edu]
Sent: Friday, July 30, 2004 10:49 AM
To: Miller, James V (Research)
Cc: Zachary Pincus; insight-users List
Subject: RE: [Insight-users] Finding out when a neighborhood iterator is
o utside the image?


One possibility is to use the NeighborhoodIterator::GetIndex(offset)  
method to return the image index of the offset and then query the
Image::RequestedRegion::IsInside(index) method to determine if that index
is within the bounds of the image.

Josh.


On Fri, 30 Jul 2004, Miller, James V (Research) wrote:

> Josh, 
> 
> I think Zach is interested in knowing when an offest within a
> Neighborhood is in bounds or not. When the neighborhood overlaps
> the boundary, there are still inbounds pixels within the 
> neighborhood that he can perform his calculations (inter pixel
> statistics).
> 
> Jim
> 
> 
> 
> -----Original Message-----
> From: Joshua Cates [mailto:cates at sci.utah.edu]
> Sent: Thursday, July 29, 2004 4:02 PM
> To: Zachary Pincus
> Cc: insight-users List
> Subject: Re: [Insight-users] Finding out when a neighborhood iterator is
> outside the image?
> 
> 
> Hi Zach,
> 
> There is a method common to all NeighborhoodIterators called InBounds()  
> that returns false when the neighborhood overlaps the boundary.  This
> method is relatively slow, however, so I don't recommend using it unless
> you are doing sparse access into the image.  If you are just sampling
> points here and there in the image, then this method shouldn't add too
> much overhead.
> 
> 
> Josh.
> 
> 
> On Thu, 29 Jul 2004, Zachary Pincus wrote:
> 
> > Hello,
> > 
> > I seem to recall seeing somewhere a method in ITK for determining when 
> > a particular element of a neighborhood (or shaped neighborhood) is 
> > outside of the real image. Unfortunately, neither searching the list 
> > nor wracking my brain can retrieve this information.
> > 
> > Basically, I'm using shaped neighborhoods to get pairs of pixels to do 
> > statistics on. Previously, I had just used the BoundaryFacesCalculator 
> > to get the region of an image where a given neighborhood could not 
> > possibly be outside the image. The problem is that just using that 
> > region is too conservative: there are parts of the image where a given 
> > neighborhood center and offset are still both on the image, even though 
> > other parts of the neighborhood might be dangling off.
> > 
> > Maybe the best thing here would be to create a 
> > "ThrowExceptionBoundaryCondition" and then catch the exception when 
> > necessary to determine whether a given pixel is actually outside of the 
> > image. Would that work, or are there other better ideas?
> > 
> > 
> > Zach Pincus
> > 
> > Department of Biochemistry and Program in Biomedical Informatics
> > Stanford University School of Medicine
> > 
> > _______________________________________________
> > Insight-users mailing list
> > Insight-users at itk.org
> > http://www.itk.org/mailman/listinfo/insight-users
> > 
> 
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