[Insight-users] ExtractFilter on VectorImage

[Luis Ibanez]

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
> 
>