[Insight-users] loss of spacing and origin when feeding an itkImage to itkWriter

[Luis Ibanez]

Hi Peter,

If you image was taken as the output of an ITK filter,
you shouldn't change the image metadata directly
(e.g. origin, spacing, direction).

Instead, you should use the
ChangeInformationImageFilter:
http://www.itk.org/Insight/Doxygen/html/classitk_1_1ChangeInformationImageFilter.html

Something like :

   changeFilter->SetInput( reader->GetOutput() );
   changeFilter->SetOutputOrigin( newOrigin );
   changeFilter->ChangOriginOn();

Otherwise, the changes that you are applying manually
to your image will get lost as soon as a call to Update()
is made in any filter downstream the pipeline.

Output images are "own" by the filter that compute
them.


BTW, please note that changing image information in a
      clinical environment is a *very dangerous* thing
      to do. You shoud really be very sure that you
      want to override the image metadata.



    Regards,


       Luis


---------------------------
Boettcher, Dr. Peter wrote:
> I have problems feeding an itkImage to itkWriter. During that process 
> the parameters image spacing and image origin are lost!
> 
>  
> 
> During my image pipeline I define image = caster->GetOutput().
> 
>  
> 
> caster2D->Update();
> 
> imageCastFix = caster2D->GetOutput();
> 
>  
> 
> Then I do some changes to the image spacing and origin:
> 
>  
> 
>   imageCastFix->SetOrigin(origin2D);
>   imageCastFix->SetSpacing(spacing2D);
>   imageCastFix->Modified();
> 
>  
> 
> Checking whether the changes were made
> 
>  
> 
> imageCastFix->Print( std::cout );
> 
>  
> 
> …
> 
> Spacing 0.576 0.576 0.576
> 
> Origin: -124.5 -124.5 -124.5
> 
> …
> 
>  
> 
> Up to this point every thing works as I expected. The image spacing and 
> origin I changes manually was assigned to the image.
> 
>  
> 
> However when I feed the modified image to an ImageWriter
> 
>  
> 
> writerFluo->SetInput( imageCastFix);
> 
> writerFluo ->Update();
> 
>  
> 
> The image file written onto my disk has an image spacing of 1 1 1 and 
> origin 0 0 0.
> 
>  
> 
> Any idea why the parameters of my image are not passed to the image writer?
> 
> This effect is independent of the image file type I define.
> 
>  
> 
> Regards, Peter.
> 
>  
> 
> 
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> 
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