ImageDataToQImage

VTKEx/Cxx/Qt/ImageDataToQImage

Description¶

This example shows how a vtkImageData can be converted into a QImage.

Seealso

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code¶

ImageDataToQImage.cxx

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

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

// 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;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ImageDataToQImage)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel 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 ()

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

If VTK is 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 ..

Build the project:

make

and run it:

./ImageDataToQImage

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.