[Insight-developers] Bug in ExtractImageFilter

[Kevin H. Hobbs]

On Fri, 2009-10-16 at 09:32 -0400, Bradley Lowekamp wrote:
> Hello Kevin,
> 

Thank you for looking into this.

> 
> This is not a bug. 

Somehow I just don't buy it.

Changing the region to be extracted just seems like such a fundamental
change to this filter that the filter should know that it needs to look
upstream to see if it can get the new region.

> If you change the methods used to invoke the pipeline execution from
> Update to UpdateLargestPossibleRegion it should work. 

You're right that does work.

It makes me feel dirty though. Like I'm asking the filter to extract my
sub region, then a few lines later telling it to get the whole image.

> It comes down to an old requested region staying around and not being
> updated. 

And that doesn't sound like a bug to you?

> So you could also use the SetRequestedRegionToLargestPossibleRegion
> before each Update methods is called. 

I don't know how to make that work.

Neither :

extract->SetExtractionRegion( region );
image->SetRequestedRegionToLargestPossibleRegion();

nor :

extract->SetExtractionRegion( region );
extract->GetOutput()->SetRequestedRegionToLargestPossibleRegion();

works. What are you suggesting I try?

Again, I have a negative emotional reaction to this. 

When a user sets the region to be extracted the user is literally
requesting a region.

I just don't see any user then writing a command that by it's name is
asking for some other region.

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