Method ApplyTransform

IO/ExportPDF/vtkPDFContextDevice2D.cxx:2232–2278

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//------------------------------------------------------------------------------
void vtkPDFContextDevice2D::ApplyTransform()
{
  // The HPDF API for transform management is lacking. There's no clear way
  // to simply *set* the transform, we can only concatenate multiple transforms
  // together. Nor is there a way to push/pop a matrix stack. So we'll just
  // invert the current transform to unapply it before applying the new one.
  HPDF_TransMatrix oldTrans = HPDF_Page_GetTransMatrix(this->Impl->Page);
  double oldInvTransMat3[9];
  vtkPDFContextDevice2D::HPDFTransformToMatrix3(
    oldTrans.a, oldTrans.b, oldTrans.c, oldTrans.d, oldTrans.x, oldTrans.y, oldInvTransMat3);
  vtkMatrix3x3::Invert(oldInvTransMat3, oldInvTransMat3);

  // Multiply the inverse current transform with the new one:
  double newTransMat3[9];
  double* mat = this->Matrix->GetMatrix()->GetData();
  vtkPDFContextDevice2D::Matrix4ToMatrix3(mat, newTransMat3);

  vtkMatrix3x3::Multiply3x3(oldInvTransMat3, newTransMat3, newTransMat3);

  // Test if the new transform is identity, within tolerance:
  bool isIdentity = true;
  constexpr double tol = 1e-6;
  for (size_t i = 0; i < 3 && isIdentity; ++i)
  {
    for (size_t j = 0; j < 3 && isIdentity; ++j)
    {
      const double val = newTransMat3[i * 3 + j];
      const double exp = (i == j) ? 1. : 0.;
      if (std::fabs(val - exp) > tol)
      {
        isIdentity = false;
      }
    }
  }

  // Do nothing if the transform would have no effect.
  if (isIdentity)
  {
    return;
  }

  // Otherwise, write the new transform out.
  float hpdfMat[6];
  vtkPDFContextDevice2D::Matrix3ToHPDFTransform(newTransMat3, hpdfMat);
  HPDF_Page_Concat(
    this->Impl->Page, hpdfMat[0], hpdfMat[1], hpdfMat[2], hpdfMat[3], hpdfMat[4], hpdfMat[5]);
}

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vtkVector2f vtkPDFContextDevice2D::GetUnscaledPenWidth()