VTK/Examples/Cxx/Qt/ImageDataToQImage

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Revision as of 14:39, 29 November 2016 by Waldyrious (talk | contribs) (greatly simplify the code, reducing the example to the bare functional minimum (tested locally); add description; use template for cmakelists)
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This example shows how a vtkImageData can be converted into a QImage.

See also the QImageToImageSource example.

ImageDataToQImage.cxx

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

#include <QImage>
#include <QApplication>

vtkSmartPointer<vtkImageData> createDemoImageData()
{
  // Create an image data
  vtkSmartPointer<vtkImageData> image = vtkSmartPointer<vtkImageData>::New();
  image->SetDimensions( 50, 50, 1 );
#if VTK_MAJOR_VERSION <= 5
  #pragma message( VTK_MAJOR_VERSION )
  image->SetNumberOfScalarComponents( 3 );
  image->SetScalarTypeToUnsignedChar();
  image->AllocateScalars();
#else
  image->AllocateScalars( VTK_UNSIGNED_CHAR, 3 );
#endif

  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;
}

QImage vtkImageDataToQImage( 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() );

  // mirror vertically
  for (int row = 0; row < height; ++row)
    {
    for (int col = 0; col < width; ++col)
      {
      // Swap rgb
      *( rgbPtr++ ) = QColor( colorsPtr[0], colorsPtr[1], colorsPtr[2] ).rgb();
      colorsPtr += 3;
      }
    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;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
 
if(POLICY CMP0020)
  cmake_policy(SET CMP0020 NEW)
endif()

PROJECT(ImageDataToQImage)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

if(${VTK_VERSION} VERSION_GREATER "6" AND VTK_QT_VERSION VERSION_GREATER "4")
  # Instruct CMake to run moc automatically when needed.
  set(CMAKE_AUTOMOC ON)
  find_package(Qt5Widgets REQUIRED QUIET)
else()
  find_package(Qt4 REQUIRED)
  include(${QT_USE_FILE})
endif()

include_directories(${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DIR})

file(GLOB UI_FILES *.ui)
file(GLOB QT_WRAP *.h)
file(GLOB CXX_FILES *.cxx)

if(${VTK_VERSION} VERSION_GREATER "6" AND VTK_QT_VERSION VERSION_GREATER "4")
  qt5_wrap_ui(UISrcs ${UI_FILES} )
  # CMAKE_AUTOMOC in ON so the MOC headers will be automatically wrapped.
  add_executable(ImageDataToQImage MACOSX_BUNDLE
    ${CXX_FILES} ${UISrcs} ${QT_WRAP})
  qt5_use_modules(ImageDataToQImage Core Gui)
  target_link_libraries(ImageDataToQImage ${VTK_LIBRARIES})
else()
  QT4_WRAP_UI(UISrcs ${UI_FILES})
  QT4_WRAP_CPP(MOCSrcs ${QT_WRAP})
  add_executable(ImageDataToQImage MACOSX_BUNDLE ${CXX_FILES} ${UISrcs} ${MOCSrcs})

  if(VTK_LIBRARIES)
    if(${VTK_VERSION} VERSION_LESS "6")
      target_link_libraries(ImageDataToQImage ${VTK_LIBRARIES} QVTK)
    else()
      target_link_libraries(ImageDataToQImage ${VTK_LIBRARIES})
    endif()
  else()
    target_link_libraries(ImageDataToQImage vtkHybrid QVTK vtkViews ${QT_LIBRARIES})
  endif()
endif()

Download and Build ImageDataToQImage

Click here to download ImageDataToQImage. and its CMakeLists.txt file.

Once the tarball ImageDataToQImage.tar has been downloaded and extracted,

cd ImageDataToQImage/build

This example requires Qt and VTK.

  • If VTK and Qt are installed:
cmake ..
  • If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
  • If Qt is not found on your system, you will need to tell CMake where to find qmake:
cmake -DQT_QMAKE_EXECUTABLE:FILEPATH=/usr/something/qmake  ..

Build the project:

make

and run it:

./ImageDataToQImage

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time. You may also need to add a Qt related path.