ImageTranslateExtent

Description¶

If you are looking to change the extent to change the "origin" of the image from the corner to the center, see vtkImageChangeInformation in CenterAnImage.

Currently this method changes the extent (shown by the terminal output in the example), but does not change where the corner of the image is displayed relative to the sphere at (0,0,0).

Question

If you have a question about this example, please use the VTK Discourse Forum

Code¶

ImageTranslateExtent.cxx

#include <vtkActor.h>
#include <vtkImageData.h>
#include <vtkImageSlice.h>
#include <vtkImageSliceMapper.h>
#include <vtkImageTranslateExtent.h>
#include <vtkInteractorStyleImage.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>

namespace {
void CreateColorImage(vtkImageData* const);
}

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkImageData> colorImage;
  CreateColorImage(
      colorImage); // This image has (0,0) at the bottom left corner

  int extent[6];
  colorImage->GetExtent(extent);
  std::cout << "Old extent: " << extent[0] << " " << extent[1] << " "
            << extent[2] << " " << extent[3] << " " << extent[4] << " "
            << extent[5] << std::endl;

  // This moves the (0,0) position in the image to the center of the image
  // colorImage->SetExtent(extent[0] - (extent[1] - extent[0]) / 2,
  //                      extent[0] + (extent[1] - extent[0]) / 2,
  //                      extent[2] - (extent[3] - extent[2]) / 2,
  //                      extent[2] + (extent[3] - extent[2]) / 2,
  //                      extent[4] - (extent[5] - extent[4]) / 2,
  //                      extent[4] + (extent[5] - extent[4]) / 2);

  int dimensions[3];
  colorImage->GetDimensions(dimensions);

  vtkNew<vtkImageTranslateExtent> translateExtent;
  translateExtent->SetTranslation(-dimensions[0] / 2, -dimensions[1] / 2, 0);
  translateExtent->SetInputData(colorImage);
  translateExtent->Update();
  colorImage->DeepCopy(translateExtent->GetOutput());

  colorImage->GetExtent(extent);
  std::cout << "New extent: " << extent[0] << " " << extent[1] << " "
            << extent[2] << " " << extent[3] << " " << extent[4] << " "
            << extent[5] << std::endl;

  vtkNew<vtkSphereSource> sphereSource;
  sphereSource->SetCenter(0.0, 0.0, 0.0);
  sphereSource->SetRadius(1.0);
  sphereSource->Update();

  vtkNew<vtkPolyDataMapper> sphereMapper;
  sphereMapper->SetInputConnection(sphereSource->GetOutputPort());

  vtkNew<vtkActor> sphereActor;
  sphereActor->SetMapper(sphereMapper);
  sphereActor->GetProperty()->SetColor(
      colors->GetColor3d("PeachPuff").GetData());

  vtkNew<vtkImageSliceMapper> imageSliceMapper;
  imageSliceMapper->SetInputData(colorImage);

  vtkNew<vtkImageSlice> imageSlice;
  imageSlice->SetMapper(imageSliceMapper);
  imageSlice->SetPosition(0, 0, 0);

  // Setup renderers
  vtkNew<vtkRenderer> renderer;
  renderer->AddViewProp(imageSlice);
  renderer->AddViewProp(sphereActor);
  renderer->ResetCamera();
  renderer->SetBackground(colors->GetColor3d("SteelBlue").GetData());

  // Setup render window
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(300, 300);
  renderWindow->AddRenderer(renderer);

  // Setup render window interactor
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;

  vtkNew<vtkInteractorStyleImage> style;

  renderWindowInteractor->SetInteractorStyle(style);

  // Render and start interaction
  renderWindow->SetWindowName("ImageTranslateExtent");

  renderWindow->Render();
  renderWindowInteractor->SetRenderWindow(renderWindow);
  renderWindowInteractor->Initialize();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

namespace {

void CreateColorImage(vtkImageData* const image)
{
  image->SetDimensions(10, 10, 1);
  image->AllocateScalars(VTK_UNSIGNED_CHAR, 3);

  vtkNew<vtkNamedColors> colors;
  unsigned char r, g, b, a;
  colors->GetColor("Thistle", r, g, b, a);

  for (unsigned int x = 0; x < 10; x++)
  {
    for (unsigned int y = 0; y < 10; y++)
    {
      unsigned char* pixel =
          static_cast<unsigned char*>(image->GetScalarPointer(x, y, 0));
      pixel[0] = r;
      pixel[1] = g;
      pixel[2] = b;
    }
  }
}

} // namespace

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ImageTranslateExtent)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  FiltersSources
  ImagingCore
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageTranslateExtent: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ImageTranslateExtent MACOSX_BUNDLE ImageTranslateExtent.cxx )
  target_link_libraries(ImageTranslateExtent PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ImageTranslateExtent
  MODULES ${VTK_LIBRARIES}
)

Download and Build ImageTranslateExtent¶

Click here to download ImageTranslateExtent and its CMakeLists.txt file. Once the tarball ImageTranslateExtent.tar has been downloaded and extracted,

cd ImageTranslateExtent/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:

./ImageTranslateExtent

WINDOWS USERS

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