[Insight-users] ShiftScaleImageFilter Bug

[Luis Ibanez]

Hi Andy,

Thanks for pointing this out.

Yes, this is a knonwn bug of the documentation.
(that is, in the Software Guide).

The ShiftScale filter is actually shifting first and scaling
after shifting. Note that the Doxygen documentation
is consistent with what the filter actually does.

The comment of the Software Guide has already been fixed
in the file

        Insight/Examples/Filtering/
                        CastingImageFilters.cxx


Note that there are several filters that will apply linear
transformation to the intensities of the input image.
For example:

       RescaleIntensityImageFilter
       NormalizeImageFilter
       IntensityWindowingImageFilter

and of course you can always write your own, by
simply deriving from the UnaryFunctorImageFilter.


Please let us know if you find any other problems

  Thanks


     Luis


-------------------------
Andy Eow wrote:

> Hi,
>  
> According to the software guide, ShiftScaleImageFilter is suppose to 
> perform the following operation:
>  
> OutputPixel = InputPixel * Scale + Shift
>  
> However, the code in itkShiftScaleImageFilter.txx does the opposite 
> instead:
>  
> value = (static_cast<RealType>(it.Get()) + m_Shift) * m_Scale;
>  
> Is this a bug? It does make a lot more sense for the multiplication 
> operation to take place first before the scalar shift.
>  
> Cheers,
> Andy
>
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