RescaleAnImage

VTKExamples/Cxx/ImageProcessing/RescaleAnImage

Question

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Code

RescaleAnImage.cxx

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

static void CreateImage(vtkImageData* const image);

int main(int, char *[])
{
  vtkSmartPointer<vtkImageData> image = vtkSmartPointer<vtkImageData>::New();
  CreateImage(image);

  vtkSmartPointer<vtkImageShiftScale> shiftScaleFilter =
    vtkSmartPointer<vtkImageShiftScale>::New();
  shiftScaleFilter->SetOutputScalarTypeToUnsignedChar();
  shiftScaleFilter->SetInputData(image);
  shiftScaleFilter->SetShift(-1.0f * image->GetScalarRange()[0]); // brings the lower bound to 0
  float 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;
  float newRange = 255; // We want the output [0,255]

  shiftScaleFilter->SetScale(newRange/oldRange);
  shiftScaleFilter->Update();

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

void CreateImage(vtkImageData* const image)
{
  // 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] =vtkMath::Random(0.0,2000.0);
      }
    }
  }
}

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.