Method PrepareImageData

IO/ExportPDF/vtkPDFContextDevice2D.cxx:1857–1925

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vtkImageData* vtkPDFContextDevice2D::PrepareImageData(vtkImageData* in)
{
  int numComps = in->GetNumberOfScalarComponents();

  // We'll only handle RGB / RGBA:
  if (numComps != 3 && numComps != 4)
  {
    vtkWarningMacro("Images with " << numComps << " components not supported.");
    return nullptr;
  }

  // Need to convert scalar type?
  if (in->GetScalarType() != VTK_UNSIGNED_CHAR)
  {
    vtkNew<vtkImageCast> cast;
    cast->SetInputData(in);
    cast->SetOutputScalarTypeToUnsignedChar();
    cast->Update();
    in = cast->GetOutput();
    in->Register(this);
  }
  else
  {
    in->Register(this); // Keep refcounts consistent
  }

  if (in->GetNumberOfScalarComponents() == 4)
  { // If RGBA, blend into brush color -- Haru doesn't support RGBA.

    vtkNew<vtkImageData> background;
    { // Fill the background image with brush color, saturate alpha
      std::array<unsigned char, 4> bgColor;
      this->Brush->GetColor(bgColor.data());
      bgColor[3] = 255; // Saturate alpha
      background->SetExtent(in->GetExtent());
      background->AllocateScalars(VTK_UNSIGNED_CHAR, 4);
      auto* scalars = vtkUnsignedCharArray::SafeDownCast(background->GetPointData()->GetScalars());
      for (int comp = 0; comp < 4; ++comp)
      {
        scalars->FillComponent(comp, bgColor[comp]);
      }
    }

    // Blend the input image over the background color:
    vtkNew<vtkImageBlend> blender;
    blender->AddInputData(0, background);
    blender->AddInputData(0, in);
    in->UnRegister(this); // Remove ref++ from above
    blender->SetBlendModeToNormal();

    vtkNew<vtkImageExtractComponents> extract;
    extract->SetInputConnection(blender->GetOutputPort(0));
    extract->SetComponents(0, 1, 2);
    extract->Update();
    in = extract->GetOutput();
    in->Register(this);
  }