[Insight-users] RequestedRegion vs RegionOfInterestImageFilte r

[Miller, James V (Research)]

Mathias,

You are correct that a filter may override the setting of RequestedRegion.  
A filter is allowed to do this if it cannot guarentee that it can produce 
the correct result by processing just the original RequestedRegion.  For 
instance, the connectivity based filters cannot guarentee they will 
get the correct segmentation if they are restricted to a particular 
requested region.  The segmentation could conceivable leave the
RequestedRegion
and loop back in.

What you are trying to do, however, is reasonable since you are allowing the

user or application to apply soem higher level knowledge of how big the 
object of interest is.  So in this case, an ExtractImageFilter or
RegionOfInterestImageFilter can be used to pull out just the piece of the
image you want to operate on.  In either case, the memory will have to be
copied.

Jim



> -----Original Message-----
> From: Mathias Seitel [mailto:mathias . seitel at igd . fhg . de]
> Sent: Saturday, July 19, 2003 4:37 AM
> To: ITK Mailing List
> Subject: [Insight-users] RequestedRegion vs 
> RegionOfInterestImageFilter
> 
> 
> Hello all,
> 
> I'm currently looking for a way to force any image filter not 
> to use the 
> whole of it's input image, but only a user-defined portion of 
> it. So far 
> I understood that the RequestedRegion of an image could be 
> used or this 
> purpose but I just found that this approach doesn't work in 
> all cases, 
> e.g. the ConnectedThresholdImageFilter automatically sets the 
> RequestedRegion to its LargestPossibleRegion. Am I right?
> 
> What I now have in mind is to interpose an ExtractImageFilter or an 
> RegionOfInterestImageFilter between the concerned image and 
> the filter. 
> One obvious drawback here is the additional memory consumption. Is it 
> possible to preserve any specified RequestedRegion, or is there some 
> other way to address the above problem? Btw. the reason why I want to 
> implement this is to have a simple way to limit a segmentation 
> algorithm, e.g. region growing, to a strict area.
> 
> Thanks,
> Mathias
> 
> 
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