void runBSplineTransform(MatlabImportFilter::Pointer matlabImport,
MatlabExportFilter::Pointer matlabExport) {
// retrieve pointers to the inputs that we are going to need here
typedef MatlabImportFilter::MatlabInputPointer MatlabInputPointer;
MatlabInputPointer inX = matlabImport->GetRegisteredInput("X");
MatlabInputPointer inY = matlabImport->GetRegisteredInput("Y");
MatlabInputPointer inXI = matlabImport->GetRegisteredInput("XI");
MatlabInputPointer inORDER = matlabImport->GetRegisteredInput("ORDER");
MatlabInputPointer inLEVELS = matlabImport->GetRegisteredInput("LEVELS");
// register the output for this function at the export filter
typedef MatlabExportFilter::MatlabOutputPointer MatlabOutputPointer;
MatlabOutputPointer outYI = matlabExport->RegisterOutput(OUT_YI, "YI");
// spline order (input argument): default or user-provided
unsigned int splineOrder = matlabImport->ReadScalarFromMatlab<unsigned int>(inORDER, 3);
// number of levels (input argument): default or user-provided
unsigned int numOfLevels = matlabImport->ReadScalarFromMatlab<unsigned int>(inLEVELS, 5);
// get size of input arguments
mwSize Mx = mxGetM(inX->pm); // number of source points
mwSize Mxi = mxGetM(inXI->pm); // number of points to be warped
// pointers to input matrices
TScalarType *x
= (TScalarType *)mxGetData(inX->pm); // source points
TScalarType *y
= (TScalarType *)mxGetData(inY->pm); // target points
TScalarType *xi
= (TScalarType *)mxGetData(inXI->pm); // points to be warped
if (x == NULL) {
mexErrMsgTxt("Cannot get a pointer to input X");
}
if (y == NULL) {
mexErrMsgTxt("Cannot get a pointer to input Y");
}
if (xi == NULL) {
mexErrMsgTxt("Cannot get a pointer to input XI");
}
// type definitions for the BSPline transform
typedef itk::Vector<TScalarType, Dimension> DataType;
typedef itk::PointSet<DataType, Dimension> PointSetType;
typedef itk::Image<DataType, Dimension> ImageType;
typedef typename
itk::BSplineScatteredDataPointSetToImageFilter<PointSetType,
ImageType> TransformType;
// variables to store the input points
typename PointSetType::Pointer pointSet = PointSetType::New();
typename PointSetType::PointType xParam;
DataType v; // v = y-x, i.e. displacement vector between source and
// target landmark
// init variables to contain the limits of a bounding box that
// contains all the points
typename ImageType::PointType orig, term;
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
orig[CAST2MWSIZE(col)] = std::numeric_limits<TScalarType>::max();
term[CAST2MWSIZE(col)] = std::numeric_limits<TScalarType>::min();
}
// find bounding box limits
for (mwSize row=0; row < Mx; ++row) {
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
orig[CAST2MWSIZE(col)] = std::min((TScalarType)orig[CAST2MWSIZE(col)], x[Mx * col + row]);
term[CAST2MWSIZE(col)] = std::max((TScalarType)term[CAST2MWSIZE(col)], x[Mx * col + row]);
orig[CAST2MWSIZE(col)] = std::min((TScalarType)orig[CAST2MWSIZE(col)], y[Mx * col + row]);
term[CAST2MWSIZE(col)] = std::max((TScalarType)term[CAST2MWSIZE(col)], y[Mx * col + row]);
}
}
for (mwSize row=0; row < Mxi; ++row) {
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
orig[CAST2MWSIZE(col)] = std::min((TScalarType)orig[CAST2MWSIZE(col)], xi[Mxi * col + row]);
term[CAST2MWSIZE(col)] = std::max((TScalarType)term[CAST2MWSIZE(col)], xi[Mxi * col + row]);
}
}
// compute length of each size of the bounding box
DataType len = term - orig;
TScalarType lenmax = std::numeric_limits<TScalarType>::min();
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
lenmax = std::max(lenmax, len[CAST2MWSIZE(col)]);
}
// duplicate the input x and y matrices to PointSet format so that
// we can pass it to the ITK function
//
// we also translate and scale all points so that the bounding box
// fits within the domain [0, 1] x [0, 1] x [0,1]. We need to do
// this because the BSpline function requires the parametric domain
// to be within [0, 1] x [0, 1] x [0,1]
for (mwSize row=0; row < Mx; ++row) {
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
v[CAST2MWSIZE(col)] = (y[Mx * col + row] - x[Mx * col + row]) / lenmax;
xParam[CAST2MWSIZE(col)] = (x[Mx * col + row] - orig[CAST2MWSIZE(col)]) / lenmax;
}
pointSet->SetPoint(row, xParam);
pointSet->SetPointData(row, v);
}
// instantiate and set-up transform
typename TransformType::Pointer transform = TransformType::New();
transform->SetGenerateOutputImage(false);
transform->SetInput(pointSet);
transform->SetSplineOrder(splineOrder);
typename TransformType::ArrayType ncps ;
ncps.Fill(splineOrder + 1);
transform->SetNumberOfControlPoints(ncps);
transform->SetNumberOfLevels(numOfLevels);
// note that closedim, spacing, sz and orig are all refered to the
// parametric domain, i.e. the domain of x and xi
typename TransformType::ArrayType closedim;
typename ImageType::SpacingType spacing;
typename ImageType::SizeType sz;
// the parametric domain is not periodic in any dimension
closedim.Fill(0);
// as we are not creating the image, we don't need to provide a
// sensible number of voxels. But size has to be at least 2 voxels
// to avoid a run-time error
sz.Fill(2);
// because the parameterization is in [0, 1] x [0, 1] x [0,1], and
// we have only size = 2 voxels in every dimension, the spacing will
// be 1.0 / (2 - 1) = 1.0
spacing.Fill(1.0);
// because of the reparameterization, the origin we have to pass to
// the transform is not the origin of the real points, but the
// origin of the [0, 1] x [0, 1] x [0,1] bounding box
typename ImageType::PointType origZero;
origZero.Fill(0.0);
transform->SetCloseDimension(closedim);
transform->SetSize(sz);
transform->SetSpacing(spacing);
transform->SetOrigin(origZero);
// run transform
transform->Update();
// create output vector and pointer to populate it
mwSize ndimxi = mxGetNumberOfDimensions(inXI->pm);
const mwSize *dimsxi = mxGetDimensions(inXI->pm);
std::vector<mwSize> size;
for (mwIndex i = 0; i < ndimxi; ++i) {
size.push_back(dimsxi[i]);
}
TScalarType *yi
= matlabExport->AllocateNDArrayInMatlab<TScalarType>(outYI, size);
// from ITK v4.x, we need to instantiate a function to evaluate
// points of the B-spline, as the Evaluate() method has been removed
// from the TransformType
#if ITK_VERSION_MAJOR>=4
// Note: in the following, we have to use TCoordRep=double, because
// ITK gives a compilation error of an abstract class not having
// been implemented. Otherwise, we would use
// TCoordRep=TScalar=float, as in the rest of this program
typedef typename
itk::BSplineControlPointImageFunction<ImageType, double> EvalFunctionType;
typename EvalFunctionType::Pointer function = EvalFunctionType::New();
function->SetSplineOrder(splineOrder);
function->SetOrigin(origZero);
function->SetSpacing(spacing);
function->SetSize(sz);
function->SetInputImage(transform->GetPhiLattice());
#endif
// sample the warp field
DataType vi; // warp field sample
typename PointSetType::PointType xiParam; // sampling coordinates
for (mwSize row=0; row < Mxi; ++row) {
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
xiParam[CAST2MWSIZE(col)] = (xi[Mxi * col + row] - orig[CAST2MWSIZE(col)]) / lenmax;
}
#if ITK_VERSION_MAJOR<4
transform->Evaluate(xiParam, vi);
#else
vi = function->Evaluate(xiParam);
#endif
for (mwSize col=0; col < (mwSize)Dimension; ++col) {
yi[Mxi * col + row] = xi[Mxi * col + row] + vi[CAST2MWSIZE(col)] * lenmax;
}
}
// exit function
return;
}
