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RescaleAnImage

vtk-examples/Cxx/ImageProcessing/RescaleAnImage

Question

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Code

RescaleAnImage.cxx

#include <vtkImageData.h>
#include <vtkImageShiftScale.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNew.h>

namespace {
void CreateImage(vtkImageData* const image,
                 vtkMinimalStandardRandomSequence* rng);
}

int main(int, char*[])
{
  vtkNew<vtkMinimalStandardRandomSequence> rng;
  rng->SetSeed(8775070);
  // rng->SetSeed(0);

  vtkNew<vtkImageData> image;
  CreateImage(image, rng);

  vtkNew<vtkImageShiftScale> shiftScaleFilter;
  shiftScaleFilter->SetOutputScalarTypeToUnsignedChar();
  shiftScaleFilter->SetInputData(image);
  shiftScaleFilter->SetShift(
      -1.0 * image->GetScalarRange()[0]); // brings the lower bound to 0
  double oldRange = image->GetScalarRange()[1] - image->GetScalarRange()[0];
  std::cout << "Old range: [" << image->GetScalarRange()[0] << ", "
            << image->GetScalarRange()[1] << "]" << std::endl;
  std::cout << "Old range magnitude: " << oldRange << std::endl;
  double newRange = 255; // We want the output [0,255]
  shiftScaleFilter->SetScale(newRange / oldRange);
  shiftScaleFilter->Update();

  std::cout << "New range: ["
            << shiftScaleFilter->GetOutput()->GetScalarRange()[0] << ", "
            << shiftScaleFilter->GetOutput()->GetScalarRange()[1] << "]"
            << std::endl;

  return EXIT_SUCCESS;
}

namespace {

void CreateImage(vtkImageData* const image,
                 vtkMinimalStandardRandomSequence* rng)
{
  // Specify the size of the image data
  image->SetDimensions(2, 3, 1);
  image->AllocateScalars(VTK_DOUBLE, 1);

  int* dims = image->GetDimensions();

  std::cout << "Dims: "
            << " x: " << dims[0] << " y: " << dims[1] << " z: " << dims[2]
            << std::endl;

  for (int z = 0; z < dims[2]; z++)
  {
    for (int y = 0; y < dims[1]; y++)
    {
      for (int x = 0; x < dims[0]; x++)
      {
        double* pixel = static_cast<double*>(image->GetScalarPointer(x, y, z));
        pixel[0] = rng->GetRangeValue(0.0, 2000.0);
        rng->Next();
      }
    }
  }
}

} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(RescaleAnImage)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkImagingCore
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping RescaleAnImage: ${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(RescaleAnImage MACOSX_BUNDLE RescaleAnImage.cxx )
  target_link_libraries(RescaleAnImage PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(RescaleAnImage MACOSX_BUNDLE RescaleAnImage.cxx )
  target_link_libraries(RescaleAnImage PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS RescaleAnImage
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build RescaleAnImage

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

cd RescaleAnImage/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:

./RescaleAnImage

WINDOWS USERS

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