[Insight-users] extract slice from RGB image

[Juan Vidal]

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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> http://www.kitware.com/products/protraining.html
>
> Please keep messages on-topic and check the ITK FAQ at:
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-- 
Juan Vidal Allende
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