VTK/Examples/Cxx/Visualization/ImageTransparency

#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkLookupTable.h>
#include <vtkImageData.h>
#include <vtkImageMapper3D.h>
#include <vtkImageMapToColors.h>
#include <vtkJPEGReader.h>
#include <vtkPointData.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleImage.h>
#include <vtkRenderer.h>
#include <vtkImageActor.h>
 
static void CreateImage(vtkSmartPointer<vtkImageData> image);
 
int main(int, char*[])
{
  vtkSmartPointer<vtkImageData> image =
    vtkSmartPointer<vtkImageData>::New();
  CreateImage(image);
 
  // Create actor
  vtkSmartPointer<vtkImageActor> imageActor =
    vtkSmartPointer<vtkImageActor>::New();
#if VTK_MAJOR_VERSION <= 5
  imageActor->SetInput(image);
#else
  imageActor->GetMapper()->SetInputData(image);
#endif
 
  // Visualize
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderer->AddActor(imageActor);
  renderer->ResetCamera();
 
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
 
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  vtkSmartPointer<vtkInteractorStyleImage> style =
    vtkSmartPointer<vtkInteractorStyleImage>::New();
 
  renderWindowInteractor->SetInteractorStyle(style);
 
  renderWindowInteractor->SetRenderWindow(renderWindow);
  renderWindowInteractor->Initialize();
  renderWindowInteractor->Start();
 
  return EXIT_SUCCESS;
}
 
void CreateImage(vtkSmartPointer<vtkImageData> image)
{
  // Specify the size of the image data
  image->SetDimensions(10,10,1);
#if VTK_MAJOR_VERSION <= 5
  image->SetNumberOfScalarComponents(4);
  image->SetScalarTypeToUnsignedChar();
#else
  image->AllocateScalars(VTK_UNSIGNED_CHAR,4);
#endif
  int* dims = image->GetDimensions();
  // int dims[3]; // can't do this
 
  std::cout << "Dims: " << " x: " << dims[0] << " y: " << dims[1] << " z: " << dims[2] << std::endl;
 
  // Fill every entry of the image with "2"
  for (int y = 0; y < dims[1]; y++)
    {
    for (int x = 0; x < dims[0]; x++)
      {
 
      unsigned char* pixel = static_cast<unsigned char*>(image->GetScalarPointer(x,y,0));
      pixel[0] = 255;
      pixel[1] = 255;
      pixel[2] = 255;
      if(x<5)
        {
        pixel[3] = 0;
        }
      else
        {
        pixel[3] = 255;
        }
      }
    }
 
}