[Insight-developers] Bug in ExtractImageFilter

[Bradley Lowekamp]

Hello Kevin,

This is not a bug. If you change the methods used to invoke the  
pipeline execution from Update to UpdateLargestPossibleRegion it  
should work. It comes down to an old requested region staying around  
and not being updated. So you could also use the  
SetRequestedRegionToLargestPossibleRegion before each Update methods  
is called.

Interestingly enough, I believe that this issue does not occur with  
the writers because the writer's output is not a DataObject and the  
requested region is not pipelined the same way.

In case you are curious this oddity is the result of code in  
ImageBase::UpdateOutputInformation:

   // Now we should know what our largest possible region is. If our
   // requested region was not set yet, (or has been set to something
   // invalid - with no data in it ) then set it to the largest possible
   // region.
   if ( this->GetRequestedRegion().GetNumberOfPixels() == 0)
     {
     this->SetRequestedRegionToLargestPossibleRegion();
     }

Brad

On Oct 15, 2009, at 4:46 PM, Kevin H. Hobbs wrote:

> I believe there is a bug in ExtractImageFilter.
>
> The attached code demonstrates the bug.
>
> All it does is creates a small image.
> Extracts a small region.
> Extracts another small region.
>
> During the second update the extract image filter throws an exception
> and claims that the requested region is outside of the largest  
> possible
> region of the input image.
>
> I'll file a bug report if you all think I should be able to change the
> region the filter extracts.
> <CMakeLists.txt><ExtractBug.cxx><signature.asc><ATT00001..txt>

========================================================
Bradley Lowekamp
Lockheed Martin Contractor for
Office of High Performance Computing and Communications
National Library of Medicine
blowekamp at mail.nih.gov


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