[Insight-users] Filtering all channels of a VectorImage

[David Doria]

On Wed, Apr 27, 2011 at 8:57 AM, Bradley Lowekamp <blowekamp at mail.nih.gov>wrote:

> Hello David,
>
> We are implementing this independent per component filtering in SimpleITK
> for VectorImages.
>
> I am curious as to what filters you are finding it useful to run on a per
> component basis, so that we can try to get those implemented in SimpleITK.
>
> Here is a sample of how we are doing it, it sounds like the same way you
> are doing it:
>
> template <class TImageType> Image
> LogImageFilter::ExecuteInternalVectorImage ( const Image& inImage1 )
> {
>   // Define the input and output image types
>   typedef TImageType
>                              InputImageType;
>   typedef typename InputImageType::InternalPixelType
>   ComponentType;
>
>   typedef typename itk::Image<ComponentType,
> InputImageType::ImageDimension> ComponentImageType;
>
>   typedef InputImageType OutputImageType;
>
>   // Get the pointer to the ITK image contained in image1
>   typename InputImageType::ConstPointer image1 =
>     dynamic_cast <const InputImageType*> ( inImage1.GetImageBase() );
>
>   // Check that ITK image pointer was properly retrieved
>   if ( image1.IsNull() )
>     {
>     sitkExceptionMacro( "Unexpected template dispatch error!" );
>     }
>
>   typedef itk::VectorIndexSelectionCastImageFilter< InputImageType,
> OutputImageType > ComponentExtratorType;
>   typename ComponentExtratorType::Pointer extractor =
> ComponentExtratorType::New();
>   extractor->SetInput( image1 );
>
>   typedef itk::ImageToVectorImageFilter<ComponentImageType>
> ToVectorFilterType;
>   typename ToVectorFilterType::Pointer toVector =
> ToVectorFilterType::New();
>
>   unsigned int numComps = image1->GetNumberOfComponentsPerPixel();
>   for ( unsigned int i = 0; i < numComps; ++i )
>     {
>     extractor->SetIndex( i );
>     extractor->Update();
>
>     Image tmp = this->ExecuteInternal<ComponentImageType>( Image(
> extractor->GetOutput() ) );
>
>     typename ComponentImageType::ConstPointer tempITKImage =
>       dynamic_cast <const ComponentImageType*> ( tmp.GetImageBase() );
>
>     toVector->SetNthInput( i, tempITKImage );
>     }
>
>   toVector->Update();
>
>   return Image( toVector->GetOutput() );
> }
>

I've needed it on RescaleImageIntensity, smoothing, logical operations (as
sometimes a "binary/mask" image is really an RGB image with each channel
identical), thresholding, etc.

I would go as far as to say all filters should be able to do this (without
writing the loop in each one). I'm going to take a look at Juliens solution
now.

David
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