int
main(int, char *[])
{
using PixelType = float;
RandomSourceType::Pointer randomImageSource = RandomSourceType::New();
randomImageSource->SetNumberOfWorkUnits(1);
randomImageSource->SetSize(bigSize);
randomImageSource->GetOutput()->SetRequestedRegion(smallSize);
std::cout << "Created random image." << std::endl;
DerivativeImageFilterType::Pointer derivativeFilter = DerivativeImageFilterType::New();
derivativeFilter->SetInput(randomImageSource->GetOutput());
derivativeFilter->SetDirection(0);
derivativeFilter->GetOutput()->SetRequestedRegion(smallSize);
derivativeFilter->Update();
std::cout << "Computed derivative." << std::endl;
return EXIT_SUCCESS;
}