[Community] [Insight-users] Cast itkImage to Matlab emxArray

[Bradley Lowekamp]

Hello,

The GetBufferPointer is a method, and I would try to avoid that in a tight loop.

Here is a recent implementation to efficiently copy ITK regions:
https://github.com/Kitware/ITK/blob/master/Modules/Core/Common/include/itkImageAlgorithm.hxx#L137

We have found that std::copy is a very robust and efficient way to copy the buffers with modern compilers. It can even work when a conversion is needed.

If you have validated the buffer is continuous and is the correct type and size. I would recommend just getting the raw buffer pointer and using std::copy. It may be up  to 10-100X faster than your implementation below.


On Oct 18, 2013, at 11:28 AM, Luca Tersi <lucatersi at gmail.com> wrote:

> Hi,
> 
> I've included some algorithms developed with Matlab in my C++ software. The Matlab algorithms were translated to C++ using Matlab Coder.
> I've some images that have to be passed back and forth from the itk pipeline to the Matlab algorithm that work with emxArray data type.
> I've made the following methods in order to copy the data, but is there any better and faster method? Moreover, is it better to use iterators or access the buffer directly?
> 
> void ImageProcessing::CopyItkToMatlabImage(ImageProcessing::RealImageType::Pointer itkI, emxArray_real_T *matlabI)
> {
>   RealImageType::SizeType size = itkI->GetLargestPossibleRegion().GetSize();
> 
>   for (int ii=0; ii < size[0]; ++ii)
>     for (int jj=0; jj < size[1]; ++jj)
>       {
>         matlabI->data[ii*size[0]+jj] = (real_T)itkI->GetBufferPointer()[ii*size[0]+jj];
>       }
> }
> 
> 
> 
> void ImageProcessing::CopyMatlabToItkImage(emxArray_real_T * matlabI, ImageProcessing::RealImageType::Pointer itkI)
> {
> 
>   int32_T *size = matlabI->size;
>   RealIteratorType out ( itkI, itkI->GetLargestPossibleRegion() );
>   out.GoToBegin();
> 
>   for (int ii=0; ii < size[0]; ++ii)
>     for (int jj=0; jj < size[1]; ++jj)
>       {
>         out.Set(matlabI->data[ii*size[0]+jj]);
>         ++out;
>       }
> }
> 
> Thanks a lot
> 
> Luca
> 
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