[Insight-users] Confusion about update sequence and required region

[Atwood, Robert C]

Hi everyone:
I want to have a region extracted from a larger image, and to have subsampled images of this region at some different resolutions. However, I keep getting 'invalid region request' exeptions on the second time I subsample the extracted region. 
How should the required region be re-set? it always works the first time no matter what the value of r_iter, within reason (2-16, even integers) so I guess that some region from the first time through is propagated to the second time


Here is simplified code I used to test without all teh other stuff going on . I am pretty sure the region extraction has worked correctly so that inputImage is a valid ImageType::Pointer

Thanks
Robert
 





typedef itk::ShrinkImageFilter<ImageType,ImageType> ShrinkerType;
...
 ShrinkerType::Pointer fshrinker = ShrinkerType::New ();
 r_iter = 4;
...

           fshrinker->SetShrinkFactors (r_iter);
           fshrinker->SetInput (inputImage);
        
         try {
           fshrinker->Update ();
         } catch (itk::ExceptionObject & err) {
           std::cerr << "ExceptionObject caught fshrinker !" << std::endl;
           std::cerr << fshrinker << std::endl;
           std::cerr << "Quitting" << std::endl;
           std::cerr << err << std::endl;
           return -1;
         }

         fshrinker->SetShrinkFactors (r_iter >> 1);
         fshrinker->SetInput (inputImage);
       try {
           fshrinker->Update ();
         } catch (itk::ExceptionObject & err) {
           std::cerr << "ExceptionObject caught fshrinker 2 !" << std::endl;
           std::cerr << fshrinker << std::endl;
           std::cerr << "Quitting" << std::endl;
           std::cerr << err << std::endl;
           return -1;
         }

...


Output
ExceptionObject caught fshrinker 2 !
ShrinkImageFilter (0x85422f0)
  RTTI typeinfo:   itk::ShrinkImageFilter<itk::Image<float, 3u>, itk::Image<float, 3u> >
  Reference Count: 2
  Modified Time: 370
  Debug: Off
  Observers: 
    none
  Number Of Required Inputs: 1
  Number Of Required Outputs: 1
  Number Of Threads: 2
  ReleaseDataFlag: Off
  ReleaseDataBeforeUpdateFlag: Off
  Input 0: (0x8520490)
  Output 0: (0x85449c0)
  AbortGenerateData: Off
  Progress: 1
  Multithreader: 
    RTTI typeinfo:   itk::MultiThreader
    Reference Count: 1
    Modified Time: 90
    Debug: Off
    Observers: 
      none
    Thread Count: 2
    Global Maximum Number Of Threads: 0
  Shrink Factor: 2 2 2 

Quitting

itk::InvalidRequestedRegionError (0x8562e00)
Location: "virtual void itk::DataObject::PropagateRequestedRegion()" 
File: /sources/local/ITK_cvs/Code/Common/itkDataObject.cxx
Line: 397
Description: Requested region is (at least partially) outside the largest possible region.



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