[Insight-users] ApproximateSignedDistanceMapImageFilter

[Luis Ibanez]

Hi Juan Carlos,

Thanks for pointing this out.

The exception is originated from

Insight/Code/Algorithms/
    itkIsoContourDistanceImageFilter.txx

lines 319-341:


        norm = vcl_sqrt((float)norm);

        if (norm > NumericTraits<PixelType>::min())
          {
          ....
          }
        else
          {
          itkExceptionMacro(<<"Gradient norm is lower than pixel precision");
          }


And the value of NumericTraits<float>::min() is = 1.17549e-38

While NumericTraits<unsigned short>::min() is = 0

Please try adding:

   std::cout << "norm = " << norm << std::endl;

to line 338 just before the exception, so that the code looks
like


 else
    {
    std::cout << "norm = " << norm << std::endl;
    itkExceptionMacro(<<"Gradient norm is lower than pixel precision");
    }

run it again, and let us know what
value of "norm" you find.


The exception seems to be there in order to avoid
a division by zero in line 323.


It will look like this class expects that input image
to have a ramp of intensity around the iso-contour
value.   Is that the case for your input image ?


     Please let us know,


          Thanks


                 Luis


----------------------------------------------------------
On Thu, Apr 8, 2010 at 10:38 AM, Juan Carlos Prieto
<juanprietob at gmail.com> wrote:
> Hello Luis and ITK Users
>
> I'm trying to use the ApproximateSignedDistanceMapImageFilter.
> As described in the documentation it says the output has to be of type
> float, When this is done, i get an exception :
>
> /builddir/build/BUILD/InsightToolkit-3.16.0/Code/Common/itkMultiThreader.cxx:475:
>
> itk::ERROR: MultiThreader(0x9a3d050):
>
> Exception occurred during SingleMethodExecute
>
> /usr/include/InsightToolkit/Algorithms/itkIsoContourDistanceImageFilter.txx:339:
>
> itk::ERROR: IsoContourDistanceImageFilter(0x9a97d28): Gradient norm is lower
> than pixel precision
>
> On the other hand I tried with the same type of my input image (UShort) and
> it worked but the output image is not as expected.
>
>
>
> Please need some help
>
> Juan Carlos Prieto
>
>
>
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