Label Binary Regions And Get Properties

Synopsis

Label binary regions in an image and get their properties.

Results

image.png

image.png

Output:

There are 1 objects.
Object 0 has bounding box ImageRegion (0x7ff924a4e558)
Dimension: 2
Index: [6, 6]
Size: [4, 4]

Code

C++

#include "itkImage.h"
#include "itkImageFileWriter.h"
#include "itkImageRegionIterator.h"
#include "itkBinaryImageToShapeLabelMapFilter.h"

using ImageType = itk::Image<unsigned char, 2>;
static void
CreateImage(ImageType::Pointer image);

int
main(int, char *[])
{
  ImageType::Pointer image = ImageType::New();
  CreateImage(image);

  using BinaryImageToShapeLabelMapFilterType = itk::BinaryImageToShapeLabelMapFilter<ImageType>;
  BinaryImageToShapeLabelMapFilterType::Pointer binaryImageToShapeLabelMapFilter =
    BinaryImageToShapeLabelMapFilterType::New();
  binaryImageToShapeLabelMapFilter->SetInput(image);
  binaryImageToShapeLabelMapFilter->Update();

  // The output of this filter is an itk::ShapeLabelMap, which contains itk::ShapeLabelObject's
  std::cout << "There are " << binaryImageToShapeLabelMapFilter->GetOutput()->GetNumberOfLabelObjects() << " objects."
            << std::endl;

  // Loop over all of the blobs
  for (unsigned int i = 0; i < binaryImageToShapeLabelMapFilter->GetOutput()->GetNumberOfLabelObjects(); i++)
  {
    BinaryImageToShapeLabelMapFilterType::OutputImageType::LabelObjectType * labelObject =
      binaryImageToShapeLabelMapFilter->GetOutput()->GetNthLabelObject(i);
    // Output the bounding box (an example of one possible property) of the ith region
#if ITK_VERSION_MAJOR >= 4
    std::cout << "Object " << i << " has bounding box " << labelObject->GetBoundingBox() << std::endl;
#else
    std::cout << "Object " << i << " has region " << labelObject->GetRegion() << std::endl;
#endif
  }

  return EXIT_SUCCESS;
}

void
CreateImage(ImageType::Pointer image)
{
  // Create a black image with a white square
  ImageType::IndexType start;
  start.Fill(0);

  ImageType::SizeType size;
  size.Fill(20);

  ImageType::RegionType region;
  region.SetSize(size);
  region.SetIndex(start);
  image->SetRegions(region);
  image->Allocate();

  itk::ImageRegionIterator<ImageType> imageIterator(image, image->GetLargestPossibleRegion());

  // Make a square
  while (!imageIterator.IsAtEnd())
  {
    if ((imageIterator.GetIndex()[0] > 5 && imageIterator.GetIndex()[0] < 10) &&
        (imageIterator.GetIndex()[1] > 5 && imageIterator.GetIndex()[1] < 10))
    {
      imageIterator.Set(255);
    }
    else
    {
      imageIterator.Set(0);
    }

    ++imageIterator;
  }

  using WriterType = itk::ImageFileWriter<ImageType>;
  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName("image.png");
  writer->SetInput(image);
  writer->Update();
}

Classes demonstrated