[vtk-developers] vtkImageButterworth filters

[John Biddiscombe]

Please ignore this. I see on second look that the value is squared
before it passes to the pow() function, so it is correct.

JB


> -----Original Message-----
> From: vtk-developers-admin at vtk.org 
> [mailto:vtk-developers-admin at vtk.org] On Behalf Of John Biddiscombe
> Sent: 17 November 2003 12:01
> To: vtk-developers at vtk.org
> Cc: Charles Law
> Subject: [vtk-developers] vtkImageButterworth filters
> 
> 
> I see at the top of the .h files for Low (+High)pass filters that
> 
>  out(i, j) = (1 + pow(CutOff/Freq(i,j), 2*Order));
> 
> But in the cxx file the implementation is
>  sum0 = 1.0 / (1.0 + pow(sum0, (float)this->Order));
> 
> The factor of two is absent from the order in the cxx
> 
> Most texts use
> 
> H(W) = 1
>        -----------
>       (1+(F/Fc)^2n)
> 
> As opposed to just n (n being order)
> 
> This looks like a typo/mistake to me. Have I missed anything?
> 
> Thanks
> 
> JB
> _______________________________________________
> vtk-developers mailing list
> vtk-developers at vtk.org 
> http://www.vtk.org/mailman/listinfo/vtk-> developers
>