Ok, I guess that you just want to extract an RGB 2D slice from a 3D RGB image.

Then, your mistake is OutputPixelType. RGBPixels are vectors of unsigned chars, and can't be directly converted to scalars (just unsigned chars). The fastest fix could be this:

  typedef itk::Image<RGBPixelType,2>       OutputPixelType_extract_RGB;

By the way, you probably missed writer->SetFileName() in your code ;)

HTH

2011/7/1 john smith <mkitkinsightuser <at> gmail.com>

Well, to explain what I am trying to do. I have created a 3D RGB image as a result of a segmentation procedure. To create this image I had used itkLabelOverlayImageFilter.So this image was created by a greyscale image and a label image, so I get the result of the initial greyscale image and the label image with blue color. When I have tried to extract a slice from the image  I got this error
error C2440: 'static_cast' : cannot convert from 'itk::RGBPixel<TComponent>' to 'unsigned char' . I have included my code in the begining of this topic. I also cannot understand the second step very well.Why I should do something like this? What should I do for this task?

Thanks for your response

2011/7/1 Juan Vidal <juanvidalallende-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

Well, I don't know exactly what your are trying to do, but in my opinion you could probably split your problem:

1) Extract the desired 2D RGB slice from the 3D RGB image (ExtractImageFilter should work).
2) Convert the 2D RGB slice to unsigned char

The second point depends on the purpose of your application. You might want to extract one of the channels, or perhaps convert the RGB image to grayscale in some fashion...

HTH

2011/6/30 john smith <mkitkinsightuser-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

Could somebody explain in some words what must be done in order to extract a 2D slice from a RGB 3D image? I am trying to find an example (but I didn't find anything) and I am reading the docs but I am totally lost. This task may be very easy but I really need some help.
Any response would be very useful.

Thanks in advace

2011/6/30 john smith <mkitkinsightuser-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

You may have right as it should work properly.It is the first time I am working with RGB images. But what changes should be done?

Thanks for yoyr response

2011/6/30 robert tamburo <robert.tamburo-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

Do you really expect the filter to extract a 2D image of unsigned char pixels from a 3D image of RGB pixels?

On Thu, Jun 30, 2011 at 3:07 PM, john smith <mkitkinsightuser-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

Hello to all,

I am trying to read an RGB image, then use the ExtractImageFilter and finally, write the RGB slice. I have written the following code, but I get this error
error C2440: 'static_cast' : cannot convert from 'itk::RGBPixel<TComponent>' to 'unsigned char' . Do you know what I am doing wrong?

Thanks in advance

///////// code //////////////
typedef itk::RGBPixel<unsigned char> RGBPixelType;
  typedef itk::Image<RGBPixelType,3> RGBImageType;

   typedef  itk::ImageFileReader< RGBImageType > ReaderType_RGB;

     ReaderType_RGB::Pointer reader_RGB = ReaderType_RGB::New();

     reader_RGB->SetFileName( "output.hdr"  );
     reader_RGB->Update();


  typedef unsigned char       OutputPixelType_extract_RGB;
  typedef itk::Image< OutputPixelType_extract_RGB, 2 >    OutputImageType_extract_RGB;
   typedef itk::ExtractImageFilter< RGBImageType, OutputImageType_extract_RGB > FilterType_extract_RGB;
    FilterType_extract_RGB::Pointer filter_extract_RGB = FilterType_extract_RGB::New();

  RGBImageType::RegionType inputRegion =
          reader_RGB->GetOutput()->GetLargestPossibleRegion();


  RGBImageType::SizeType size = inputRegion.GetSize();
 
  // get the size of the hole 3D image
  size_x = size[0];
  size_y = size[1];
   size_z = size[2];
 
  // get slices of z coordiante
  size[2] = 0;

   RGBImageType::IndexType start = inputRegion.GetIndex();
  ui->verticalScrollBar_z->setRange(0,size_z-1);
  unsigned int sliceNumber = ui->verticalScrollBar_z->value();
  start[2] = 10;
 

  RGBImageType::RegionType desiredRegion;
  desiredRegion.SetSize( size );
  desiredRegion.SetIndex( start );

  filter_extract_RGB->SetExtractionRegion( desiredRegion );

    typedef  itk::ImageFileWriter< OutputImageType_extract_RGB  > WriterType_RGB;
     WriterType_RGB::Pointer writer_RGB = WriterType_RGB::New();
    writer_RGB->SetFileName( "z.png" );

   filter_extract_RGB->SetInput( reader_RGB->GetOutput() );
   writer_RGB->SetInput( filter_extract_RGB->GetOutput() );

    try
    {
    writer_RGB->Update();
    }
  catch( itk::ExceptionObject & err )
    {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    }

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Powered by www.kitware.com

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http://www.kitware.com/opensource/opensource.html

Kitware offers ITK Training Courses, for more information visit:
http://www.kitware.com/products/protraining.html

Please keep messages on-topic and check the ITK FAQ at:
http://www.itk.org/Wiki/ITK_FAQ

Follow this link to subscribe/unsubscribe:
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--
Juan Vidal Allende

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Juan Vidal Allende