SliceOrder

#include <vtkMatrix4x4.h>
#include <vtkNew.h>
#include <vtkSmartPointer.h>
#include <vtkStringFormatter.h>
#include <vtkTransform.h>

#include <array>
#include <map>
#include <string>
#include <vector>

namespace {

class SliceOrder
{
  // clang-format off
  /*
    These transformations permute image and other geometric data to maintain
      proper orientation regardless of the acquisition order. After applying
      these transforms with vtkTransformFilter, a view up of 0, -1, 0 will
      result in the body part facing the viewer.

NOTE: Some transformations have a -1 scale factor for one of the components.
    To ensure proper polygon orientation and normal direction,
      you must apply the vtkPolyDataNormals filter.

   Naming (the nomenclature is medical):
     si - superior to inferior (top to bottom)
     is - inferior to superior (bottom to top)
     ap - anterior to posterior (front to back)
     pa - posterior to anterior (back to front)
     lr - left to right
     rl - right to left

   */
  // clang-format on

public:
  /**
   * Generate the transforms corresponding to the slice order.
   */
  SliceOrder();

  virtual ~SliceOrder() = default;

public:
  /**
   * Returns the vtkTransform corresponding to the slice order.
   *
   * @param sliceOrder: The slice order.
   * @return The vtkTransform corresponding to the slice order.
   */
  vtkSmartPointer<vtkTransform> Get(std::string const& sliceOrder);

  /**
   * Print the homogenous matrix corresponding to the slice order.
   *
   * @param order: The slice order.
   */
  void PrintTransform(std::string const& order);

  /**
   * Print all the homogenous matrices corresponding to the slice orders.
   *
   */
  void PrintAlltransforms();

private:
  std::map<std::string, vtkSmartPointer<vtkTransform>> transform;

private:
  // Used to genrate the the homogenous matrices corresponding to the slice
  // orders.
  std::array<double, 16> si_arr{1, 0,  0, 0, 0, 0, 1, 0,
                                0, -1, 0, 0, 0, 0, 0, 1};
  std::array<double, 16> is_arr{1, 0,  0, 0, 0, 0, -1, 0,
                                0, -1, 0, 0, 0, 0, 0,  1};
  std::array<double, 16> lr_arr{0, 0, -1, 0, 0, -1, 0, 0,
                                1, 0, 0,  0, 0, 0,  0, 1};
  std::array<double, 16> rl_arr{0, 0, 1, 0, 0, -1, 0, 0,
                                1, 0, 0, 0, 0, 0,  0, 1};
  std::array<double, 16> hf_arr{-1, 0, 0,  0, 0, 1, 0, 0,
                                0,  0, -1, 0, 0, 0, 0, 1};
  // Used to print out the homogenous matrices in the order
  //  entered into the transform map.
  std::vector<std::string> sort_order{};
};

}

namespace {

SliceOrder::SliceOrder()
{
  vtkNew<vtkMatrix4x4> si_mat;
  si_mat->SetData(this->si_arr.data());

  vtkNew<vtkMatrix4x4> is_mat;
  is_mat->SetData(this->is_arr.data());

  vtkNew<vtkMatrix4x4> lr_mat;
  lr_mat->SetData(this->lr_arr.data());

  vtkNew<vtkMatrix4x4> rl_mat;
  rl_mat->SetData(this->rl_arr.data());

  // The previous transforms assume radiological views of the slices
  //  (viewed from the feet).
  // Other modalities such as physical sectioning may view from the head.
  // The following transforms modify the original with a 180° rotation
  //  about the y-axis.

  vtkNew<vtkMatrix4x4> hf_mat;
  hf_mat->SetData(this->hf_arr.data());

  vtkNew<vtkTransform> si_trans;
  si_trans->SetMatrix(si_mat);
  this->transform["si"] = si_trans;
  this->sort_order.push_back("si");

  vtkNew<vtkTransform> is_trans;
  is_trans->SetMatrix(is_mat);
  this->transform["is"] = is_trans;
  this->sort_order.push_back("is");

  vtkNew<vtkTransform> ap_trans;
  ap_trans->Scale(1, -1, 1);
  this->transform["ap"] = ap_trans;
  this->sort_order.push_back("ap");

  vtkNew<vtkTransform> pa_trans;
  pa_trans->Scale(1, -1, -1);
  this->transform["pa"] = pa_trans;
  this->sort_order.push_back("pa");

  vtkNew<vtkTransform> lr_trans;
  lr_trans->SetMatrix(lr_mat);
  this->transform["lr"] = lr_trans;
  this->sort_order.push_back("lr");

  vtkNew<vtkTransform> rl_trans;
  lr_trans->SetMatrix(rl_mat);
  this->transform["rl"] = rl_trans;
  this->sort_order.push_back("rl");

  vtkNew<vtkTransform> hf_trans;
  hf_trans->SetMatrix(hf_mat);
  this->transform["hf"] = hf_trans;
  this->sort_order.push_back("hf");

  vtkNew<vtkTransform> hf_si_trans;
  hf_si_trans->SetMatrix(hf_mat);
  hf_si_trans->Concatenate(si_mat);
  this->transform["hfsi"] = hf_si_trans;
  this->sort_order.push_back("hfsi");

  vtkNew<vtkTransform> hf_is_trans;
  hf_is_trans->SetMatrix(hf_mat);
  hf_is_trans->Concatenate(is_mat);
  this->transform["hfis"] = hf_is_trans;
  this->sort_order.push_back("hfis");

  vtkNew<vtkTransform> hf_ap_trans;
  hf_ap_trans->SetMatrix(hf_mat);
  hf_ap_trans->Scale(1, -1, 1);
  this->transform["hfap"] = hf_ap_trans;
  this->sort_order.push_back("hfap");

  vtkNew<vtkTransform> hf_pa_trans;
  hf_pa_trans->SetMatrix(hf_mat);
  hf_pa_trans->Scale(1, -1, -1);
  this->transform["hfpa"] = hf_pa_trans;
  this->sort_order.push_back("hfpa");

  vtkNew<vtkTransform> hf_lr_trans;
  hf_lr_trans->SetMatrix(hf_mat);
  hf_lr_trans->Concatenate(lr_mat);
  this->transform["hflr"] = hf_lr_trans;
  this->sort_order.push_back("hflr");

  vtkNew<vtkTransform> hf_rl_trans;
  hf_rl_trans->SetMatrix(hf_mat);
  hf_rl_trans->Concatenate(rl_mat);
  this->transform["hfrl"] = hf_rl_trans;
  this->sort_order.push_back("hfrl");

  // Identity
  this->transform["I"] = vtkNew<vtkTransform>();
  this->sort_order.push_back("I");

  // Zero
  vtkNew<vtkTransform> z_trans;
  z_trans->Scale(0, 0, 0);
  this->transform["Z"] = z_trans;
  this->sort_order.push_back("Z");
}

void SliceOrder::PrintTransform(std::string const& order)
{
  auto m = this->transform[order]->GetMatrix();
  vtk::println(order);
  for (int i = 0; i < 4; ++i)
  {
    for (int j = 0; j < 4; ++j)
    {
      if (j < 3)
      {
        vtk::print("{:>6.2g}", m->GetElement(i, j));
      }
      else
      {
        vtk::println("{:>6.2g}", m->GetElement(i, j));
      }
    }
  }
}

void SliceOrder::PrintAlltransforms()
{
  for (auto const& k : this->sort_order)
  {
    PrintTransform(k);
  }
}

vtkSmartPointer<vtkTransform> SliceOrder::Get(std::string const& sliceOrder)
{
  return this->transform[sliceOrder];
}

} // namespace

  SliceOrder so;
  // so.PrintAlltransforms();