[Insight-users] ExtractFilter on VectorImage

[Karthik Krishnan]

Thanks for the report. Fixed in CVS HEAD.

http://www.itk.org/cgi-bin/viewcvs.cgi/Code/Common/itkImageBase.h?root=Insight&r1=1.65&r2=1.66
http://www.itk.org/cgi-bin/viewcvs.cgi/Code/Common/itkVectorImage.h?rev=1.12&root=Insight&view=log
http://www.itk.org/cgi-bin/viewcvs.cgi/Code/BasicFilters/itkExtractImageFilter.txx?rev=1.21&root=Insight&view=log

As Luis mentioned, the VectorLength meta-data wasn't propagating down 
the pipeline.

The default implementation ProcessObject::GenerateOutputInformation() is 
responsible for propagating meta-data to the output. This does propagate 
all meta-data, including the VectorLength to the output. Most filters 
use the default implementaton or call the superclass method. However, a 
few filters override this method. For instance the ExtractImageFilter, 
which must provide its own method cause the input and output images 
could be of different dimensions ! These filters should have an extra 
line that propagates VectorLength info, if any

 output->SetNumberOfComponentsPerPixel( 
input->GetNumberOfComponentsPerPixel() );

And that was just added.

Thanks
karthik


Luis Ibanez wrote:

>
> Hi Jordi
>
> Thanks for pointing this out.
>
> The support for VectorImages in all ITK filters is being introduced
> progressively. In principle, most ITK filters should work for Vector
> images, but there are many filters that have never been tried, so
> it is quite possible that you will run into some filters that do not
> manage the VectorImages correctly.
>
> In those cases, we appreciate to receive the reports, so we can fix
> those filters.
>
> What is probably happening in the ExtractImage filter is that it is
> not copying the Length from the input image into the output image.
> This copy should happen during the invocation of the CopyInformation()
> method, in the ImageBase class.
>
> We will take a look at this filter (and the closely related
> itkRegionOfInterestImageFilter) and make sure that they can be
> used for processing VectorImages,... and will let you know when
> this modifications are available in the CVS repository.
>
>
>
>
>     Regards,
>
>
>
>        Luis
>
>
>
>
> -----------------------
> Jordi Inglada wrote:
>
>> Hi,
>>
>> As suggested by Karthik as an answer to my post on multi-dimensional 
>> images, we are now using the itkVectorImage class.
>>
>> We are now facing a problem when plugging VectorImages into the 
>> itkExtractImageFilter. We use
>>
>>  typedef itk::VectorImage < PixelType, Dimension>        ImageType;
>>
>> and the pipeline is as follows :
>>
>> Reader --> ExtractFilter --> Writer
>>
>> Our first test used an RGB PNG image. Interestingly, the IO PNG 
>> ressource knows how to build a 3 channel VectorImage. Actually, if we 
>> use the very simple pipeline
>>
>> Reader --> Writer
>>
>> with the ImageType defined above, the output image is the exact copy 
>> of the input one.
>>
>> However, when the extract filter is used, the output PNG image, even 
>> if it has the right dimensions, it is empty except for some columns. 
>> In the case where I try to write it in JPEG, I get the following 
>> message : "Too many color components: 0, max 10".
>>
>> I have found a workaround by creating a VectorToRGBImageFilter which 
>> does the conversion (I wasn't able to make Adaptors work for 
>> VariableLengthVector pixels). And it works if the conversion is done 
>> BEFORE the extract filter. The output images are bad if the 
>> conversion is done AFTER the extract filter.
>>
>> By now, this solution is OK for me, but I think that this is not 
>> really satisfacttory.
>>
>> So my question is : can one use the VectorImage as any other 
>> itk::Image with itk filter, or has one to make the conversion to 
>> fixed array pixel types in order to make things work?
>>
>> Thanks.
>>
>> Jordi
>>
>>
>
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