[Insight-users] extract slice from RGB image

[john smith]

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 at gmail.com>

> 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 at gmail.com>
>
>> 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 at gmail.com>
>>
>>> 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 at gmail.com>
>>>
>>>> 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 at gmail.com
>>>> > 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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>>>>>
>>>>
>>>
>>
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>>
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>> Kitware offers ITK Training Courses, for more information visit:
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>
>
> --
> Juan Vidal Allende
>
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