[Insight-users] Insight-users Digest, Vol 61, Issue 12

Simon Warfield simon.warfield at childrens.harvard.edu
Tue May 5 21:45:51 EDT 2009

insight-users-request at itk.org wrote:
> Date: Tue, 5 May 2009 17:57:50 -0400
> From: Michel Audette <michel.audette at kitware.com>
> Subject: [Insight-users] Significant changes coming to address bug
>         6558
> To: insight-developers at itk.org, insight-users at itk.org
> Message-ID:
>         <b16f21b00905051457v68e2a634hbe83fa20a293c07f at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
> Dear members of the Insight community,
> we are currently at work to solve bug 6558: Physical coordinates of a pixel
> - Severe inconsistency and bug in ImageBase. We've found that the
> implementation of pixel-centered positions had unintended and adverse
> effects on other classes, which we have also been correcting for the past
> two days. This fix appears to be a priority of many members of the
> community, so we feel it's important to provide the required functionality
> integrally.
> We will make available a patch to the Insight community to apply and comment
> on.
> This patch can be found at: http://public.kitware.com/Bug/view.php?id=6558.
> Feel free to comment on its validity either by email or in the SecondLife
> discussions on Friday afternoons.

Dear Michel,

  Thanks for working on correcting and improving the representation of 
physical coordinates in ITK.

  The patch you reference has several good additions to the previous 
work.  I want to note a few potential problems:
1. It references vnl_math_round( ) and vnl_math_rnd()  . You should 
consistently use one rounding implementation, and it should be the one 
Tom suggested.

2. The patch has a fix for 
Code/Common/itkLinearInterpolateImageFunction.txx, the same fix needs to 
be applied to the VectorLinearInterpolateImageFunction.txx file,
       but in fact with some straightforward modifications, the 
VectorLinearInterpolateImageFunction implementation could be an empty 
shell that delegates to the regular 
itkLinearInterpolateImageFunction.txx  . See the earlier email from Tom 
on the list about that too.
      You might also notice that all of the interpolators that have an 
interpolation window size > 0 can make invalid accesses, by deliberate 
design. If you are fixing some of the interpolators, you might consider 
to fix the others also.

3. The patch introduces a new concept IsStrictlyInside() . I am not sure 
what it is for.  I suggest to have IsInside() actually test whether or 
not a point is exactly inside the region, and I suggest to not introduce 

> We plan on making the fix permanent in the upcoming release.
> Best wishes,
> Michel
> --
> Michel Audette, Ph.D.
> R & D Engineer,
> Kitware Inc.,
> Chapel Hill, N.C.


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