PERF: Reduce verbosity of itk::GaussianOperator warning

[tbirdso]

itk::GaussianOperator can be set with a MaximumKernelWidth parameter
such that a kernel that would otherwise overflow this size is cropped to
the maximum width. Cropping to the set maximum width happens frequently
in cases such as Gaussian blurring for multiscale pyramid generation and
is expected behavior, but the previous warning message makes it seem
like a failure case. This commit reduces the verbosity of the message
from a warning to a debug printout so that developers can get insights
into kernel cropping when needed, but are not alarmed by default warning
printouts.

Previous behavior: Warning whenever Gaussian kernel is correctly truncated to user specifications.

WARNING: In C:\P\IPP\ITK-source\ITK\Modules\Core\Common\include\itkGaussianOperator.hxx, line 57
GaussianOperator (000000C7587FC630): Kernel size has exceeded the specified maximum width of 32 and has been truncated to 33 elements. You can raise the maximum width using the SetMaximumKernelWidth method.

New behavior: No printout unless explicitly enabled.

PR Checklist

• No major design changes were made (or the changes have been approved)

Refer to the ITK Software Guide for
further development details if necessary.

[Leengit]

In case it is related, ... I am now getting an error message in the master branch:

Building CXX object Modules/Registration/Common/test/CMakeFiles/ITKRegistrationCommonTestDriver.dir/itkMultiResolu
tionImageRegistrationMethodTest_1.cxx.o
FAILED: Modules/Registration/Common/test/CMakeFiles/ITKRegistrationCommonTestDriver.dir/itkMultiResolutionImageRegistration
MethodTest_1.cxx.o
[munch]
In file included from ~/git/ITK/Modules/Core/Common/include/itkLightObject.h:21,
                 from ~/git/ITK/Modules/Core/Common/include/itkObject.h:31,
                 from ~/git/ITK/Modules/Core/Transform/include/itkTransformBase.h:23,
                 from ~/git/ITK/Modules/Core/Transform/include/itkTransform.h:22,
                 from ~/git/ITK/Modules/Core/Transform/include/itkBSplineBaseTransform.h:22,
                 from ~/git/ITK/Modules/Registration/Common/include/itkImageToImageMetric.h:21,
                 from ~/git/ITK/Modules/Registration/Common/include/itkMutualInformationImageToImageMetric.h:21,
                 from ~/git/ITK/Modules/Registration/Common/test/itkMultiResolutionImageRegistrationMethodTest_1.cxx:19:
~/git/ITK/Modules/Core/Common/include/itkGaussianOperator.hxx: In instantiation of ‘typename itk::GaussianOperator<TPixel, VDimension, TAllocator>::Superclass::CoefficientVector itk::GaussianOperator<TPixel, VDimension, TAllocator>::GenerateCoefficients() [with TPixel = float; unsigned int VDimension = 3; TAllocator = itk::NeighborhoodAllocator<float>; typename itk::GaussianOperator<TPixel, VDimension, TAllocator>::Superclass::CoefficientVector = std::vector<double>]’:
~/git/ITK/Modules/Core/Common/include/itkGaussianOperator.hxx:26:1:   required from here
~/git/ITK/Modules/Core/Common/include/itkMacro.h:489:17: error: ‘class itk::GaussianOperator<float, 3, itk::NeighborhoodAllocator<float> >’ has no member named ‘GetDebug’
  489 |       if (this->GetDebug() && itk::Object::GetGlobalWarningDisplay())          \
      |           ~~~~~~^~~~~~~~
~/git/ITK/Modules/Core/Common/include/itkGaussianOperator.hxx:55:7: note: in expansion of macro ‘itkDebugMacro’
   55 |       itkDebugMacro(<< "Kernel size has exceeded the specified maximum width of " << m_MaximumKernelWidth
      |       ^~~~~~~~~~~~~
~/git/ITK/Modules/Core/Common/include/itkGaussianOperator.hxx: In instantiation of ‘typename itk::GaussianOperator<TPixel, VDimension, TAllocator>::Superclass::CoefficientVector itk::GaussianOperator<TPixel, VDimension, TAllocator>::GenerateCoefficients() [with TPixel = double; unsigned int VDimension = 3; TAllocator = itk::NeighborhoodAllocator<double>; typename itk::GaussianOperator<TPixel, VDimension, TAllocator>::Superclass::CoefficientVector = std::vector<double>]’:
~/git/ITK/Modules/Core/Common/include/itkGaussianOperator.hxx:26:1:   required from here
~/git/ITK/Modules/Core/Common/include/itkMacro.h:489:17: error: ‘class itk::GaussianOperator<double, 3, itk::NeighborhoodAllocator<double> >’ has no member named ‘GetDebug’
  489 |       if (this->GetDebug() && itk::Object::GetGlobalWarningDisplay())          \
      |           ~~~~~~^~~~~~~~
~/git/ITK/Modules/Core/Common/include/itkGaussianOperator.hxx:55:7: note: in expansion of macro ‘itkDebugMacro’

[tbirdso]

It certainly appears related. Interesting that this did not show up in CI. @Leengit could you please share details on your build platform?

[Leengit]

Linux 5.13.0-41-generic #46~20.04.1-Ubuntu SMP Wed Apr 20 13:16:21 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
ninja 1.10.0

[tbirdso]

Thank you, on review I am also able to see failures in CDash Expected Nightly Builds. My guess is that this means itkDebugMacro is only valid in objects inheriting from a certain base, perhaps ProcessObject? Maybe I missed something in documentation?

I will open an issue to track. If we can't use debug printouts here I would be in favor of removing the warning message entirely. It could be useful in certain scenarios where the user is unaware of a default truncation parameter, but in general it is simply informing the user that execution is proceeding according to design.

[Leengit]

Perhaps a quick, sloppy fix to get the master branch working again. And an issue that asks that it be fixed more properly.