[Insight-users] itk::BSplineDownsampleImageFilter

[jef vdmb]

Hi,(appologies if I missed your reply)I am resending my reply concerning the BSplineDownsampleImageFitler, just in case the previous message got lost.  

Any ideas? Can I consider the 3.8 version as correct or was there a specific reason it was modified?
Thank you in advance for your help on the matter!Regards, Jef

From: jvdmb at hotmail.com
To: luis.ibanez at kitware.com
CC: insight-users at itk.org
Subject: RE: [Insight-users] itk::BSplineDownsampleImageFilter
Date: Mon, 8 Feb 2010 14:26:54 +0000








Hi Luis,
Thanks for your quick reply! I attached a screenshot to illustrate the change in behavior I observed.
As the names of the images (visible in the bottom left corner of the images) suggest, the top left picture is the input image, top right the output image when using the 3.8 version of the DownsampleImageFilter, bottom left the output image when using the 3.16 version of the DownsampleImageFilter and bottom right the output image when using the 3.16 version of the UpsampleImageFilter. 
The origin remains unchanged for all images (even with the centered coordinate system). The size and spacing of the images are, respectively:
209x155x169  2x2x2 (input)104x77x84  4x4x4 (output_downsample_3_8)104x77x84  4x4x4 (output_downsample_3_16)418x310x338  1x1x1 (output_upsample_3_16)
It seems that the images have the correct size and spacing. However based on their appearance, the  "image content" is incomplete in the case of the 3.16 version. Only half of the image is shown in the Y-dimension. This is not the case for the 3.8 version or for the upsampler. I am unable to say if these images are correct however.
Thanks,Jef   

> Date: Fri, 5 Feb 2010 12:44:59 -0500
> Subject: Re: [Insight-users] itk::BSplineDownsampleImageFilter
> From: luis.ibanez at kitware.com
> To: jvdmb at hotmail.com
> CC: insight-users at itk.org
> 
> Hi Jef,
> 
> Could you please describe in more detail what you mean by
> 
>                      "portraited half in Y -dimension?"
> 
> if you could post a screenshot that will be great.
> 
> It will help us a lot to track the potential source of the problem.
> 
> FYI, please note that one of the recent changes in ITK is that
> the coordiantes of pixels are now copmuted consistently at the
> center of the pixel. This applies to the BSpline Grids as well,
> and had an impact on what gets to be considered to be inside
> and outside of the image.
> 
> (this may or may not be related to the change in behavior that
> you are observing...)
> 
> 
> 
>       Thanks
> 
> 
>            Luis
> 
> 
> 
> ------------------------------------------------------------------
> On Thu, Feb 4, 2010 at 12:33 PM, jef vdmb <jvdmb at hotmail.com> wrote:
> > Hi,
> >
> > I am using the bspline downsample filter in the 3.16 version
> >
> >      typedef itk::BSplineResampleImageFilterBase<InputImageType,
> > InputImageType> ResamplerType;
> >      typename itk::BSplineDownsampleImageFilter<
> > InputImageType,InputImageType, ResamplerType >::Pointer df
> >           = itk::BSplineDownsampleImageFilter<
> > InputImageType,InputImageType, ResamplerType >::New();
> >         df->SetSplineOrder(3);
> >     df->SetInput(input);
> >     df->Update();
> >
> > Unless I am using this filter incorrectly, it would seem that there is a
> > problem with the filter. The output computed is wrong. The output image
> > properties are set correctly (half the size, double the spacing,...) but the
> > content of the original image is only portraited half in Y -dimension? This
> > is not the case in the 3.8 version, the filter seems to have broken
> > somewhere in between, probalby due to changes in the file
> > itkBSplineResampleImageFilterBase.txx.
> >
> > The result is the same for all resampler types:
> >
> >     typedef itk::BSplineResampleImageFilterBase<InputImageType,
> > InputImageType> ResamplerType;
> >     typedef itk::BSplineCenteredResampleImageFilterBase<InputImageType,
> > InputImageType> CenteredResamplerType;
> >     typedef itk::BSplineL2ResampleImageFilterBase<InputImageType,
> > InputImageType> L2ResamplerType;
> >     typedef itk::BSplineCenteredL2ResampleImageFilterBase<InputImageType,
> > InputImageType> CenteredL2ResamplerType;
> >
> > The Upsampler doesn't show the same issues, it works fine in both 3.16 and
> > 3.8 versions.
> >
> > Regards,
> > Jef
> >
> >
> >
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