ImageMagnify

VTKEx/Cxx/Images/ImageMagnify

Description vtkImageMagnify increases the dimensions of an image by integral magnification factors. It also adjusts the spacing of the pixels so that the magnified image covers the same region as the original image. To stretch the image, the pixel spacing needs to be adjusted. This example uses vtkImageChangeInformation to modify the magnified image's spacing. The result is an image that has increased numbers of pixels and is stretched in the magnified directions.

Question

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Code

ImageMagnify.cxx

#include <vtkImageActor.h>
#include <vtkInteractorStyleImage.h>
#include <vtkImageData.h>
#include <vtkImageMapper3D.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>
#include <vtkPNGReader.h>
#include <vtkImageMagnify.h>
#include <vtkImageChangeInformation.h>

int main(int argc, char *argv[])
{
  // Handle the arguments
  if(argc < 2)
  {
    std::cout << "Required arguments: filename.png" << std::endl;
    return EXIT_FAILURE;
  }

  // Read the image
  vtkSmartPointer<vtkPNGReader> reader =
    vtkSmartPointer<vtkPNGReader>::New();
  reader->SetFileName(argv[1]);

  // Increase the dimensions of the image
  vtkSmartPointer<vtkImageMagnify> magnifyFilter =
    vtkSmartPointer<vtkImageMagnify>::New();
  magnifyFilter->SetInputConnection(reader->GetOutputPort());
  magnifyFilter->SetMagnificationFactors(2,1,1);
  magnifyFilter->Update();

  // Adjust the spacing of the magnified image. This will stretch the
  // image
  vtkSmartPointer<vtkImageChangeInformation> changeFilter =
    vtkSmartPointer<vtkImageChangeInformation>::New();
  changeFilter->SetInputConnection(magnifyFilter->GetOutputPort());
  changeFilter->SetSpacingScale(
    magnifyFilter->GetMagnificationFactors()[0],
    magnifyFilter->GetMagnificationFactors()[1],
    magnifyFilter->GetMagnificationFactors()[2]);

  vtkSmartPointer<vtkImageActor> originalActor =
    vtkSmartPointer<vtkImageActor>::New();
  originalActor->GetMapper()->SetInputConnection(
    reader->GetOutputPort());

  vtkSmartPointer<vtkImageActor> magnifiedActor =
    vtkSmartPointer<vtkImageActor>::New();
  magnifiedActor->GetMapper()->SetInputConnection(
    changeFilter->GetOutputPort());

  // Define viewport ranges
  // (xmin, ymin, xmax, ymax)
  double originalViewport[4] = {0.0, 0.0, 0.5, 1.0};
  double magnifiedViewport[4] = {0.5, 0.0, 1.0, 1.0};

  // Setup renderers
  vtkSmartPointer<vtkRenderer> originalRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  originalRenderer->SetViewport(originalViewport);
  originalRenderer->AddActor(originalActor);
  originalRenderer->ResetCamera();
  originalRenderer->SetBackground(.4, .5, .6);

  vtkSmartPointer<vtkRenderer> magnifiedRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  magnifiedRenderer->SetViewport(magnifiedViewport);
  magnifiedRenderer->AddActor(magnifiedActor);
  magnifiedRenderer->ResetCamera();
  magnifiedRenderer->SetBackground(.4, .5, .7);

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize(600, 300);
  renderWindow->AddRenderer(originalRenderer);
  renderWindow->AddRenderer(magnifiedRenderer);

  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  vtkSmartPointer<vtkInteractorStyleImage> style =
    vtkSmartPointer<vtkInteractorStyleImage>::New();

  renderWindowInteractor->SetInteractorStyle(style);

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

  renderWindowInteractor->Start();

  return  EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ImageMagnify)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkIOImage
  vtkvtkImagingCore
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping ImageMagnify: ${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(ImageMagnify MACOSX_BUNDLE ImageMagnify.cxx )
  target_link_libraries(ImageMagnify PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ImageMagnify MACOSX_BUNDLE ImageMagnify.cxx )
  target_link_libraries(ImageMagnify PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ImageMagnify
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build ImageMagnify

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

cd ImageMagnify/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:

./ImageMagnify

WINDOWS USERS

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