ImageDataToQImage

#include <vtkImageData.h>
#include <vtkSmartPointer.h>

#include <QImage>
#include <QColor>
#include <QApplication>

// Create a green 50x50 imageData for demonstration purposes
vtkSmartPointer<vtkImageData> createDemoImageData()
{
  vtkSmartPointer<vtkImageData> image = vtkSmartPointer<vtkImageData>::New();
  image->SetDimensions( 50, 50, 1 );
  image->AllocateScalars( VTK_UNSIGNED_CHAR, 3 );

  int width = image->GetDimensions()[0];
  int height = image->GetDimensions()[1];

  for ( int y = 0; y < height; y++ )
  {
    for ( int x = 0; x < width; x++ )
    {
      unsigned char *pixel =
        static_cast<unsigned char *>( image->GetScalarPointer( x, y, 0 ) );
      pixel[0] = 0;
      pixel[1] = 255;
      pixel[2] = 0;
    }
  }

  return image;
}

// The actual conversion code
QImage vtkImageDataToQImage( vtkSmartPointer<vtkImageData> imageData )
{
  if ( !imageData ) { return QImage(); }

  /// \todo retrieve just the UpdateExtent
  int width = imageData->GetDimensions()[0];
  int height = imageData->GetDimensions()[1];
  QImage image( width, height, QImage::Format_RGB32 );
  QRgb *rgbPtr =
    reinterpret_cast<QRgb *>( image.bits() ) + width * ( height - 1 );
  unsigned char *colorsPtr =
    reinterpret_cast<unsigned char *>( imageData->GetScalarPointer() );

  // Loop over the vtkImageData contents.
  for ( int row = 0; row < height; row++ )
  {
    for ( int col = 0; col < width; col++ )
    {
      // Swap the vtkImageData RGB values with an equivalent QColor
      *( rgbPtr++ ) = QColor( colorsPtr[0], colorsPtr[1], colorsPtr[2] ).rgb();
      colorsPtr += imageData->GetNumberOfScalarComponents();
    }

    rgbPtr -= width * 2;
  }

  return image;
}

int main( int argc, char *argv[] )
{
  QApplication app( argc, argv );

  QImage qimage = vtkImageDataToQImage( createDemoImageData() );
  qimage.save( "qimage.png" );

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ImageDataToQImage)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel QUIET)
if (NOT VTK_FOUND)
  message("Skipping ImageDataToQImage: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(ImageDataToQImage MACOSX_BUNDLE ImageDataToQImage.cxx )
  target_link_libraries(ImageDataToQImage PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ImageDataToQImage MACOSX_BUNDLE ImageDataToQImage.cxx )
  target_link_libraries(ImageDataToQImage PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ImageDataToQImage
    MODULES ${VTK_LIBRARIES}
    )
endif () 

cd ImageDataToQImage/build 

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ImageDataToQImage