[Insight-users] Problem in writing vector images

[Hsieh]

Hi all,

Problem solved. The second argument in "typedef itk::VectorImage< DTIPixelType, 6>   DTIOutputImageType;" should be the dimension of the image, which is 3, instead of 6, which I thought it was the vector length.

Best regards,
Meng-Kang Hsieh (Michael)
OpSciTech, Erasmus Mundus
Delft University of Technology


-----Original Message-----
From: David Doria [mailto:daviddoria at gmail.com] 
Sent: Monday, April 11, 2011 8:07 PM
To: Hsieh
Cc: insight-users at itk.org
Subject: Re: [Insight-users] Problem in writing vector images

On Mon, Apr 11, 2011 at 9:12 AM, Hsieh <M.Hsieh at student.tudelft.nl> wrote:
> Hi all,
>
>
>
> After extracting scalar components from vector image using
> itkVectorIndexSelectionCastImageFilter.h and some image processing on each
> of them, now I want to put these scalar images back into one vector image by
> using, idea searched from the insight user archive,
> itkImageToVectorImageFilter.h, a type conversion error occurred when I tried
> to write the "VectorImage" image from the output of
> itkImageToVectorImageFilter to the image file writer.
>
> Type definition are shown:
>
> typedef itk::DiffusionTensor3D< PixelType >       DTIPixelType;
>
> typedef itk::Image< DTIPixelType, 3 >           DTIImageType;
>
>     typedef itk::VectorImage< DTIPixelType, 6>   DTIOutputImageType;
>
>      typedef itk::Image<  PixelType, 3 >          ScalarImageType;
>
> typedef itk::VectorIndexSelectionCastImageFilter< DTIImageType,
>
>                                                        ScalarImageType >
> VectorSelectType;
>
>      typedef itk::ImageToVectorImageFilter< ScalarImageType >
> VectorCombineType;
>
>
>
>      typedef itk::ImageFileReader< DTIImageType >      ReaderType;
>
>      typedef itk::ImageFileWriter< ScalarImageType >   WriterType;
>
>      typedef itk::ImageFileWriter< DTIOutputImageType >      DTIWriterType;
>
>
>
> Error:
>
> If I assign a DTIOutputImageType::Pointer for the output of the
> ImageToVectorImageFilter and feed the writer the pointer, I get this
>
> 1>.\ImageReadExportNifti4.cxx(177) : error C2440: 'initializing' : cannot
> convert from 'itk::VectorImage<TPixel,VImageDimension> *' to
> 'itk::SmartPointer<TObjectType>'
>
>
>
> If I put the output of the ImageToVectorImageFilter directly to the writer,
> I get this
>
> 1>.\ImageReadExportNifti4.cxx(178) : error C2664:
> 'itk::ImageFileWriter<TInputImage>::SetInput' : cannot convert parameter 1
> from 'itk::VectorImage<TPixel,VImageDimension> *' to 'const
> itk::VectorImage<TPixel,VImageDimension> *'
>
>
>
> I wonder if the problem is caused by the typedef of the images. I'm confused
> between "Vector" image type and "VectorImage" image type. Is there a
> specific writer for the VectorImage type? Or is there another way to do what
> I intended, combining scalar images to one vector image?
>
>
>
> Thank you in advance for your response.
>
>
>
> Best regards,
>
> Meng-Kang Hsieh (Michael)
>
> OpSciTech, Erasmus Mundus
>
> Delft University of Technology

You can write an itkVectorImage directly as long as the filename ends
in .mhd (or another format that supports vector images).

There is a brief explanation of itkVectorImage here:
http://www.itk.org/Wiki/ITK/Examples/VectorImages/VectorImage

David