ITK/Tutorials/DOs and DONTs

PipeLine

DO

• Do call Update() before using the pipeline output
• Do call UpdateLargestPossibleRegion() when reusing a reader.

        When reusing a reader you must call:
             reader->UpdateLargestPossibleRegion()
        instead of the usual:
             reader->Update()
        Otherwise the extent of the previous image is kept, and in some cases lead to Exceptions 
        being thrown if the second image is smaller than the first one.
   

Filter-Specific

itkConnectedComponentsImageFilter

DO NOT

• Do not assume InputImage->SetRequestedRegion(smallregion) will make the filter faster! The filter will run on the entire InputImage regardless.

DO

• To make it run on a smaller block:
  • get a new itkRegionOfInterestImageFilter, say ROIfilter
  • ROIfilter->SetInput(InputImage);
  • ROIfilter->SetRegionOfInterest(smallregion);
  • CCfilter->SetInput (ROIfilter->GetOutput());

Image Creation

DO

• On a newly-manually-created image, do initialize the pixel values if you expect them to be so!
  • Example: image->FillBuffer(0); // initialize it to all dark
  • ITK doesn't initialize the image buffer when you call Allocate(). It is your responsibility to initialize the pixel values.

Coding Style

DO NOT

• Do not declare constants using
  • #define CONST_VALUE_NAME 3
  • Use instead
    • const unsigned int CONST_VALUE_NAME = 3,
• ITK doesn't define constants with #defines in header files
• Do not call Delete() in an ITK smart pointer.
  • If you want to destroy a smart pointer object itksmartp, do:

          itksmartp = NULL;
  the ITK smart pointer will determine whether the object should be "deleted".

 Calling Delete() in ITK smart pointers is a common mistake
         when combining VTK code (that requires the use of Delete() )
         and ITK code, (that forbids the use of Delete() ).
         Using the new vtkSmartPointer class will help in a more consistent mindset when combining ITK and VTK code.
         Instead of:
              vtkclass * ptr = vtkclass::New();
         do:
              vtkSmartPointer< vtkclass >  ptr = vtkSmartPointer< vtkclass >::New()
         and then you won't need to call Delete() in VTK classes either.