[Insight-users] ImageAdaptor and Regions

[Nick Arini]

Luis,

I ran the experiments you suggested with the following results:

Thanks,
Nick.

Luis Ibanez wrote:

>
> Hi Nick,
>
> Please do the two following experiments:
>
> 1) Instead of calling Update() in the resampler filter
>    call UpdateLargestPossibleRegion().

RESULT:  This caused exactly the same behaviour as previously (i.e. 
exception still thrown).

>
> 2) Before calling Update() in the resampler filter, call
>    Update() directly on the reader.
>
RESULT: This fixed the problem and led to the program giving the 
expected and desired results (i.e. image loaded and rescaled correctly).

>
> 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>
>>
>> _______________________________________________
>> Insight-users mailing list
>> Insight-users at itk.org
>> http://www.itk.org/mailman/listinfo/insight-users
>>
>
>
>
>
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