[Insight-developers] Problems with resizing filter output

[Miller, James V (Research)]

Did you look at what ExpandImageFilter does for small input to 
large output case?

It overrides two methods GenerateOutputInformation() and
GenerateInputRequestedRegion().



> -----Original Message-----
> From: Kent Williams [mailto:norman-k-williams at uiowa . edu]
> Sent: Thursday, September 04, 2003 2:15 PM
> To: Insight Developers List
> Subject: [Insight-developers] Problems with resizing filter output
> 
> 
> I'm trying to implement a pair of filters for doing FFT and 
> IFFT operations, 
> the idea being that the FFT filter takes a image of real type 
> as input and 
> produces an image of complex type as output.  The IFFT does 
> the opposite.
> 
> The FFT operation's output has a smaller size than the input --  
> N div 2 + 1 complex numbers for the One-Dimensional FFT, and 
> Dim(1) x Dim(2) x 
> (Dim(n) div 2 + 1) for the general case.   So I used the 
> itk:ShrinkImageFilter as a pattern for dealing with changing 
> the output image 
> size.  itk:ShrinkImageFilter overrides 
> UpdateOutputInformation to change the 
> size of the output image, so I did the same in my FFT 
> Real-to-Complex filter 
> and IFFT Complex-to-Real filter.
> 
> Going from a large input to smaller output works fine, but 
> the converse does 
> not.  The PropagateRequestedRegion method throws an 
> exception, because it 
> wants to request an input region that's larger than the input 
> image supports.  
> Overriding UpdateOutputInformation does successfully set the 
> size of the 
> output image to be larger than the input image, but this 
> apparently has the 
> side effect of requestiong an input region the same size as 
> the larger output 
> region.
> 
> So the question is this: How do I let the filter pipeline 
> know that I only 
> need as much data as is in the smaller input Image source?
> 
> 
> 
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