[Insight-users] ImageAdaptor and Regions

[Luis Ibanez]

Hi Nick,

Please do the two following experiments:

1) Instead of calling Update() in the resampler filter
    call UpdateLargestPossibleRegion().

2) Before calling Update() in the resampler filter, call
    Update() directly on the reader.


Let us know what happens on each cases, that
will help us localize the eventual problem.


   Thanks


     Luis


---------------------
Nick Arini wrote:

> Dear Insight users,
> 
> I am trying to use an image adapter to get and rescale the individual 
> channels of an RGB image in a similar way to
> Examples/DataRepresentation/Image/ImageAdaptor2.cxx.
> 
> I then want to use an image iterator on the resulting images to access 
> the pixel values of the individual channels. I have encountered a 
> problem with defining a region (I want the whole image here) for input 
> to the iterator. This works just fine until I added the ImageAdaptor 
> stuff. I caught the exception and it tells me I am requesting a region 
> outside the largest region but as I want the whole image and it stays 
> the same size throughout I dont know why I am getting this exception. 
> The message and the code snippet are below. Can anyone enlighten me as 
> to what I have done wrong?
> 
> Thanks and best regards,
> 
> Nick
> 
> <begin exception message>
> 
>  itk::ExceptionObject (0xbfe3f9e0)
>  Location: "ImageAdaptor::PropagateRequestedRegion()"
>  File: /home/nicha/ITK_source/Insight/Code/Common/itkDataObject.cxx
>  Line: 397
>  Description: Requested region is (at least partially) outside the 
> largest possible region.
> 
> <end exception message>
> 
> 
> 
> <begin code>
> 
>    typedef  float                                                  
> ChannelPixelType;
>    typedef  itk::RGBPixel< ChannelPixelType >   RGBPixelType;
> 
> 
>    // We will need to use an adapter to make the RGB image look like a 
> scalar image for the rescaling
>    typedef itk::RedPixelAccessor< ChannelPixelType >::InternalType 
> InputPixelType;
>      typedef itk::Image< InputPixelType,  2 >  ImageType;
>    typedef itk::ImageAdaptor< ImageType, itk::RedPixelAccessor< 
> ChannelPixelType > > ImageAdaptorType;
> 
>    ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();
> 
> 
>    typedef itk::ImageFileReader< ImageType >  ReaderType;
>    ReaderType::Pointer reader = ReaderType::New();
>    reader->SetFileName( filename );
> 
> 
>    adaptor->SetImage( reader->GetOutput() );
> 
> 
>    typedef itk::Image< ChannelPixelType > OutputImageType; // the red 
> channel image type
> 
>    // Do some image rescaling here
>    typedef itk::RescaleIntensityImageFilter< ImageAdaptorType, 
> OutputImageType >  RescalerType;
>    RescalerType::Pointer rescaler = RescalerType::New();
>    rescaler->SetInput( adaptor );
>       rescaler->SetOutputMinimum( 0 );
>    rescaler->SetOutputMaximum( 255 );
> 
>    OutputImageType::Pointer image = rescaler->GetOutput();
>  
>    try
>      {
>        rescaler->Update();
>      }
>    catch( itk::ExceptionObject exp )
>      {
>        std::cout << exp << std::endl;
>      }
>      // now get the region associated with the image
>    OutputImageType::RegionType region = image->GetLargestPossibleRegion();
> 
> 
>    // And the image dimensions
>   Output ImageType::RegionType::SizeValueType width = region.GetSize(0);
>   OutputImageType::RegionType::SizeValueType height = region.GetSize(1);
> 
>    // define and construct a simple image iterator from an itk::Image    
>    typedef itk::ImageRegionConstIterator< OutputImageType > 
> ConstIteratorType;
>    ConstIteratorType constIterator( image, region );
> 
>    // Use the iterator in a loop
>    for( constIterator.GoToBegin(); !constIterator.IsAtEnd(); 
> ++constIterator )
>      {
>         float pix  =  constIterator.Get();
>      }
> 
> 
> <end code>
> 
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