[Insight-users] Using MetaImageIO to write CovariantVector signed char

[Julien Jomier]

Hi Dan,

Most of the recent compilers assume that "char" are actually "signed 
char", but some compilers refers to them as different types ("char" can 
be signed or unsigned depending on the compiler flags).

You can use the "char" type with MSVC8 which is the same as a "signed 
char". I've put a fix for this in ITK cvs so that "signed char" is 
recognized as "char".

Hope that helps,

Julien

Dan Mueller wrote:
> Hi Insight-Users,
> 
> I have a question regarding the use of the ITK MetaImageIO to write a 
> vector pixel of signed char type. The pixel type I am trying to write is 
> itk::CovariantVector< signed char, 2>. Using the MetaImageIO factory 
> (ie. output filename has .mhd extension), the following exception is thrown:
> 
> itk::ExceptionObject (0129F0A4)
> Location: "bool __thiscall itk::ImageIOBase::SetPixelTypeInfo(const 
> class type_info &)"
> File: ..\..\..\Code\IO\itkImageIOBase.cxx
> Line: 340
> Description: itk::ERROR: MetaImageIO(01778A80): Pixel type currently not 
> supported. typeid.name = class itk::CovariantVector<signed char,2>
> 
> If I change the type to signed short or char everything works fine. Is 
> there a specific reason the MetaImageIO factory classes do not support 
> writing signed char files? If not, how would I go about added support 
> for them? BTW: char is supported but not signed char, are they the same? 
> Does another IO factory support the writing of signed char vector outputs?
> 
> I have have a quick look in itkImageIOBase.cxx, but couldn't really work 
> out where to start.
> 
> I have attached my source code below for your reference. My system is as 
> follows:
>     Windows XP SP1
>     CMake 2.4.2
>     ITK 2.8.1
>     VS8.0.50727.42
> 
> Thanks for any help.
> 
> Cheers
> 
> Dan
> 
> 
> #include "itkImage.h"
> #include "itkCovariantVector.h"
> #include "itkImageFileReader.h"
> #include "itkImageFileWriter.h"
> #include "itkGradientImageFilter.h"
> #include "itkVectorCastImageFilter.h"
> 
> int main(int argc, char *argv[])
> {
>     if (argc < 3)
>     {
>         std::cerr << "Usage: " << std::endl;
>         std::cerr << argv[0];
>         std::cerr << " InputImageFilename";
>         std::cerr << " OutputImageFilename";
>         std::cerr << std::endl;
>         return EXIT_FAILURE;
>     }
> 
>     // Set input variables
>     char* InputImageFilename  = argv[1];
>     char* OutputImageFilename = argv[2];
> 
>     // Declare types
>     const unsigned int Dimension = 2;
>     typedef itk::Image< unsigned char, Dimension > InputImageType;
>     typedef itk::CovariantVector< signed char, Dimension > 
> OutputPixelTye; // Works if changed to signed short
>     typedef itk::Image< OutputPixelTye, Dimension > OutputImageType;
>     typedef itk::GradientImageFilter< InputImageType > GradientFilterType;
>     typedef GradientFilterType::OutputImageType GradientVectorImageType;
>     typedef itk::VectorCastImageFilter< GradientVectorImageType, 
> OutputImageType > VectorCastFilterType;
>     typedef itk::ImageFileReader< InputImageType > ReaderType;
>     typedef itk::ImageFileWriter< OutputImageType > WriterType;
> 
>     try
>     {
>         // Read input image
>         ReaderType::Pointer reader = ReaderType::New();
>         reader->SetFileName( InputImageFilename );
>         reader->Update();
>        
>         // Compute gradient
>         GradientFilterType::Pointer filterGrad = GradientFilterType::New();
>         filterGrad->SetInput( reader->GetOutput() );
>         filterGrad->Update();
> 
>         // Cast
>         VectorCastFilterType::Pointer filterCast = 
> VectorCastFilterType::New();
>         filterCast->SetInput( filterGrad->GetOutput() );
>         filterCast->Update();
> 
>         // Write output
>         WriterType::Pointer writer = WriterType::New();
>         writer->SetFileName( OutputImageFilename );
>         writer->SetInput( filterCast->GetOutput() );
>         writer->Update();
>     }
>     catch (itk::ExceptionObject & err)
>     {
>         std::cout << "ExceptionObject caught !" << std::endl;
>         std::cout << err << std::endl;
>         return EXIT_FAILURE;
>     }
> 
>     // Return
>     return EXIT_SUCCESS;
> }
> 
> 
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