VTK/Examples/Cxx/Images/DrawOnAnImage

#include <vtkSmartPointer.h>
 
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkJPEGReader.h>
#include <vtkImageData.h>
#include <vtkImageMapper3D.h>
#include <vtkImageViewer2.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageBlend.h>
 
int main ( int argc, char* argv[] )
{
  //Verify input arguments
  if ( argc != 2 )
    {
    std::cout << "Usage: " << argv[0]
              << " InputFilename(jpg)" << std::endl;
    return EXIT_FAILURE;
    }
 
  // Parse input arguments
  std::string inputFilename = argv[1];
 
  // Read the image
  vtkSmartPointer<vtkJPEGReader> jPEGReader = 
    vtkSmartPointer<vtkJPEGReader>::New();
  jPEGReader->SetFileName ( inputFilename.c_str() );
  jPEGReader->Update();
 
  vtkImageData* image = jPEGReader->GetOutput();
 
  // Find center of image
  int center[2];
  center[0] = (image->GetExtent()[1] + image->GetExtent()[0]) / 2;
  center[1] = (image->GetExtent()[3] + image->GetExtent()[2]) / 2;
 
  // Pick a radius for the circle
  int radius;
  radius = (image->GetExtent()[1] < image->GetExtent()[3]) ?
    image->GetExtent()[1] * 2 / 5 : image->GetExtent()[3] * 2 / 5;
 
  // Draw a circle in the center of the image
  vtkSmartPointer<vtkImageCanvasSource2D> drawing = 
    vtkSmartPointer<vtkImageCanvasSource2D>::New();
  drawing->SetNumberOfScalarComponents(3);
  drawing->SetScalarTypeToUnsignedChar();
  drawing->SetExtent(image->GetExtent());
  drawing->SetDrawColor(255.0, 255.0, 255.0);
  drawing->DrawCircle(center[0], center[1], radius);
 
  // Combine the images (blend takes multiple connections on the 0th
  // input port)
  vtkSmartPointer<vtkImageBlend> blend = 
    vtkSmartPointer<vtkImageBlend>::New();
  blend->AddInputConnection(jPEGReader->GetOutputPort());
  blend->AddInputConnection(drawing->GetOutputPort());
  blend->SetOpacity(0,.6);
  blend->SetOpacity(1,.4);
 
  // Display the result
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = 
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
 
  vtkSmartPointer<vtkImageViewer2> imageViewer = 
    vtkSmartPointer<vtkImageViewer2>::New();
  imageViewer->SetInputConnection(blend->GetOutputPort());
  imageViewer->SetSize(640, 512);
  imageViewer->SetupInteractor(renderWindowInteractor);
  imageViewer->GetRenderer()->ResetCamera();
  imageViewer->GetRenderer()->SetBackground(1,0,0); //red
 
  renderWindowInteractor->Initialize();
  renderWindowInteractor->Start();
 
  return EXIT_SUCCESS;
}