[Insight-users] Still having Problems taking a vtk dataset into itk

[Luis Ibanez]

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Hi John,

Your code looks ok for the most part.
Here are some hints that can help to get it running.

1) The VTKImageToImage and ImageToVTKImage filters
     are not really "filters" they just put together
     an itk+vtk importer and exporter and connect
     their callbacks. These are just convenience
     classes to simplify the connectivity.

     The consequence is that when you call Update()
     on them, nothing happens. You may have to call
     their method "GetImporter()" and on the importer
     filter call "Update()".

     This is not a concern when you plug them in a
     pipeline since in this case the actual two internal
     filters are the ones that become plugged in.
     So, all the update calls propagate normally.

     Now that, this is not the reason for your code
     to fail. It simply explains something about the
     debugging output you are getting. The two Update()
     calls on the vtk+itk connectors have to be seen
     as null operations.

2)  When running your code in an actual TIFF image
     I found an exception thrown indicating that the
     input TIFF image has four components and the output
     is supposed to be only one. (like a grayscale image).

     The importer/exporter  are not supporting color
     images at this point. If you actually want to
     process color images, you could get around this
     limitation by converting your TIFF image to PNG
     or MetaImage color format and then using the native
     ITK ImageFileReader that is capable of reading
     color images from this formats into an image of
     type:

     itk::Image< itk::RGBPixel< unsigned char > , 2 >

     You will find an example on reading writing
     color images on the SoftwareGuide.pdf in section 6.2

     The associated example is in

      Insight/Examples/IO/


3) As an easy test, I replaced your vtkTIFF reader
    and writer with PNG ones, and provided a grayscale
    image as input. For example:

     Insight/Examples/Data/BrainProtonDensitySlice.png

    With this change the code is running fine.


Please find attached the modified .cxx file.


Let us know if you have further questions.


   Thanks


     Luis


--------------------------------------
John David Fleig wrote:
 > We updated our copy of itk through cvs here and I tried the following
 > code:
 >
 >   typedef itk::Image<unsigned char,2> CharType;
 >
 >   vtkTIFFReader* imageReader = vtkTIFFReader::New();
 >   imageReader->SetFileName("Wrath.tif");
 >   imageReader->Update();
 >
 >   imageReader->Print(cerr);
 >



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#include "itkImage.h"
#include "itkVTKImageToImageFilter.h"
#include "itkImageToVTKImageFilter.h"
#include "itkRGBAPixel.h"

#include "vtkTIFFWriter.h"
#include "vtkImageCast.h"
#include "vtkTIFFReader.h"

#include "vtkPNGWriter.h"
#include "vtkPNGReader.h"

int main()
{

 typedef unsigned char PixelType;

 typedef itk::Image< PixelType, 2 > CharType;

  vtkPNGReader* imageReader = vtkPNGReader::New();
  imageReader->SetFileName("test.png"); 

  typedef itk::VTKImageToImageFilter<CharType> ImporterToITK;
  ImporterToITK::Pointer movingItkImporter = ImporterToITK::New();
  movingItkImporter->SetInput(imageReader->GetOutput());
  movingItkImporter->Update();  // <---- Does nothing !

  typedef itk::ImageToVTKImageFilter<CharType> ImporterToVTK;
  ImporterToVTK::Pointer vtkimporter = ImporterToVTK::New();
  vtkimporter->SetInput( movingItkImporter->GetOutput() );
  vtkimporter->Update(); // << --- Does nothing !

  vtkImageCast *caster = vtkImageCast::New();
  caster->SetInput( vtkimporter->GetOutput() );
  caster->SetOutputScalarTypeToUnsignedChar();

  vtkPNGWriter* imageWriter = vtkPNGWriter::New();
  imageWriter->SetInput(caster->GetOutput());
  imageWriter->SetFileName("test_copy.png");

  try {
     imageWriter->Write();  // Triggers the pipeline execution
  }
  catch( itk::ExceptionObject & exp )
  {
    std::cerr << "Exception caught" << std::endl;
    std::cerr << exp << std::endl;
  }
  
  


  return 0;
  }

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