ENH: add a convenience function WriteImage

[dzenanz]

Inspired by #2102 and dzenanz/ITKMorphologicalContourInterpolation@a9ac128.

PR Checklist

• No API changes were made (or the changes have been approved)
• No major design changes were made (or the changes have been approved)
• Added test (or behavior not changed)
• Updated API documentation (or API not changed)
• Added license to new files (if any)
• Added Python wrapping to new files (if any) as described in ITK Software Guide Section 9.5
• Added ITK examples for all new major features (if any)

[blowekamp]

Please consider placing these procedural methods into a sub-namespace of itk.

Also consider just using the std::string methods. C strings can implicitly be converted to std::string. So the raw C ptr is just for efficiency (?), but this a convince function for code that should not be time critical, so the burden of the extra methods out ways the potential enhancement.

[N-Dekker]

It seems to me that the const char * overloads aren't necessary, as @blowekamp said.

[dzenanz]

Good point Brad! I will also wait for review from Niels. Hans merged it too fast.

[N-Dekker]

So the raw C ptr is just for efficiency (?), but this a convince function for code that should not be time critical, so the burden of the extra methods out ways the potential enhancement.

I agree. By the way, if the performance penalty of creating an std::string would be a serious problem (not in this case, I think) C++17 introduces std::string_view, which is more lightweight than std::string. That's for later, possibly... 😃

[N-Dekker]

Please consider placing these procedural methods into a sub-namespace of itk.

Of course, that is why I originally proposed defining the function as a static member function of ImageFileWriter<>. #2102 So that it wouldn't look like a function without a home 😺 But I'm not really opposed to having it as a free function at itk namespace level, if that's what you want. I have to say it is quite convenient to have it at itk namespace.

[hjmjohnson]

Good point Brad! I will also wait for a review from Niels. Hans merged it too fast.

Sorry, I'm just trying to keep the forward momentum. This topic had many discussions and I thought it represented a good step forward.

BTW: I agree with the proposed changes to drop const char *. The std::string_view would be a great candidate for macro.

# a macro to take advantage of newer C++ standards when available
#if C++17 
   using ITK_STRING_VIEW=std::string_view
#else
   using ITK_STRING_VIEW=std::string
#endif

[N-Dekker]

Technically I wouldn't think that an overload for non-const TImage * should be necessary, when there is already an overload for const TImage *. Did you encounter any case where the non-const TImage * overload appeared necessary?

[N-Dekker]

It looks like the const SmartPointer<const TImage> overloads may also be removed, as the compiler may deduce the constness of TImage automatically for the SmartPointer<TImage> overload. (For example, TImage could be deduced to const itk::Image<int>.)

[dzenanz]

Without non-const overloads there are compile errors:

4>itkImageRandomIteratorTest2.cxx
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkImageRandomIteratorTest2.cxx(85): error C2672: 'itk::WriteImage': no matching overloaded function found
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkImageRandomIteratorTest2.cxx(85): error C2784: 'void itk::WriteImage(const itk::SmartPointer<const TImage>,const itk::ITK_STRING_VIEW &,bool)': could not deduce template argument for 'const itk::SmartPointer<const TImage>' from 'itk::SmartPointer<itk::Image<PixelType,2>>'
4>c:\dev\itk-git\modules\io\imagebase\include\itkImageFileWriter.h(260): note: see declaration of 'itk::WriteImage'
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkImageRandomIteratorTest2.cxx(85): error C2784: 'void itk::WriteImage(const TImage *,const itk::ITK_STRING_VIEW &,bool)': could not deduce template argument for 'const TImage *' from 'itk::SmartPointer<itk::Image<PixelType,2>>'
4>c:\dev\itk-git\modules\io\imagebase\include\itkImageFileWriter.h(249): note: see declaration of 'itk::WriteImage'
4>itkSymmetricSecondRankTensorImageReadTest.cxx
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkSymmetricSecondRankTensorImageReadTest.cxx(87): error C2672: 'itk::WriteImage': no matching overloaded function found
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkSymmetricSecondRankTensorImageReadTest.cxx(87): error C2784: 'void itk::WriteImage(const itk::SmartPointer<const TImage>,const itk::ITK_STRING_VIEW &,bool)': could not deduce template argument for 'const itk::SmartPointer<const TImage>' from 'itk::SmartPointer<itk::Image<MatrixPixelType,3>>'
4>c:\dev\itk-git\modules\io\imagebase\include\itkImageFileWriter.h(260): note: see declaration of 'itk::WriteImage'
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkSymmetricSecondRankTensorImageReadTest.cxx(87): error C2784: 'void itk::WriteImage(const TImage *,const itk::ITK_STRING_VIEW &,bool)': could not deduce template argument for 'const TImage *' from 'itk::SmartPointer<itk::Image<MatrixPixelType,3>>'
4>c:\dev\itk-git\modules\io\imagebase\include\itkImageFileWriter.h(249): note: see declaration of 'itk::WriteImage'
4>itkSymmetricSecondRankTensorImageWriteReadTest.cxx
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkSymmetricSecondRankTensorImageWriteReadTest.cxx(72): error C2672: 'itk::WriteImage': no matching overloaded function found
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkSymmetricSecondRankTensorImageWriteReadTest.cxx(72): error C2784: 'void itk::WriteImage(const itk::SmartPointer<const TImage>,const itk::ITK_STRING_VIEW &,bool)': could not deduce template argument for 'const itk::SmartPointer<const TImage>' from 'itk::SmartPointer<itk::Image<TensorPixelType,2>>'
4>c:\dev\itk-git\modules\io\imagebase\include\itkImageFileWriter.h(260): note: see declaration of 'itk::WriteImage'
4>C:\Dev\ITK-git\Modules\Core\Common\test\itkSymmetricSecondRankTensorImageWriteReadTest.cxx(72): error C2784: 'void itk::WriteImage(const TImage *,const itk::ITK_STRING_VIEW &,bool)': could not deduce template argument for 'const TImage *' from 'itk::SmartPointer<itk::Image<TensorPixelType,2>>'
4>c:\dev\itk-git\modules\io\imagebase\include\itkImageFileWriter.h(249): note: see declaration of 'itk::WriteImage'

[N-Dekker]

Is itk::ITK_STRING_VIEW already there? How is it defined?