Valued Regional Minimal Image

Synopsis

Valued regional minimal of an image.

Results

input.png

output.png

Code

C++

#include "itkImage.h"
#include "itkImageFileWriter.h"
#include "itkValuedRegionalMinimaImageFilter.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 ValuedRegionalMinimaImageFilter = itk::ValuedRegionalMinimaImageFilter<ImageType, ImageType>;

  ValuedRegionalMinimaImageFilter::Pointer filter = ValuedRegionalMinimaImageFilter::New();
  filter->SetInput(image);

  using WriterType = itk::ImageFileWriter<ImageType>;
  WriterType::Pointer writer = WriterType::New();

  writer->SetFileName("input.png");
  writer->SetInput(image);
  writer->Update();

  writer->SetFileName("output.png");
  writer->SetInput(filter->GetOutput());
  writer->Update();

  return EXIT_SUCCESS;
}

void
CreateImage(ImageType::Pointer image)
{
  // Create an image with 2 connected components
  ImageType::RegionType region;
  ImageType::IndexType  start;
  start[0] = 0;
  start[1] = 0;

  ImageType::SizeType size;
  unsigned int        NumRows = 200;
  unsigned int        NumCols = 300;
  size[0] = NumCols;
  size[1] = NumRows;

  region.SetSize(size);
  region.SetIndex(start);

  image->SetRegions(region);
  image->Allocate();

  // Make two intensity blobs
  for (unsigned int r = 0; r < NumRows; r++)
  {
    for (unsigned int c = 0; c < NumCols; c++)
    {
      ImageType::IndexType pixelIndex;
      pixelIndex[0] = c;
      pixelIndex[1] = r;

      double c1 = c - 100.0;
      double c2 = c - 200.0;

      double rr = r - 100.0;

      double v1 = 200.0 - std::sqrt(rr * rr + c1 * c1);
      double v2 = 150.0 - std::sqrt(rr * rr + c2 * c2);

      if (v1 > 190.0)
        v1 = 190.0;
      if (v2 > 140.0)
        v2 = 140.0;

      double maxv = v1;
      if (maxv < v2)
        maxv = v2;

      double val = maxv;

      if (val < 0.0)
        val = 0.0;
      if (val > 255.0)
        val = 255.0;

      if (c < 5)
        val = 255.0;

      image->SetPixel(pixelIndex, static_cast<unsigned char>(val));
    }
  }
}

Classes demonstrated

template<typename TInputImage, typename TOutputImage>
class ValuedRegionalMinimaImageFilter : public itk::ValuedRegionalExtremaImageFilter<TInputImage, TOutputImage, std::less<TInputImage::PixelType>, std::less<TOutputImage::PixelType>>

Transforms the image so that any pixel that is not a regional minima is set to the maximum value for the pixel type. Pixels that are regional minima retain their value.

Regional minima are flat zones surrounded by pixels of higher value. A completely flat image will be marked as a regional minima by this filter.

This code was contributed in the Insight Journal paper: “Finding regional extrema - methods and performance” by Beare R., Lehmann G. https://www.insight-journal.org/browse/publication/65

Author

Richard Beare. Department of Medicine, Monash University, Melbourne, Australia.

See

ValuedRegionalMaximaImageFilter, ValuedRegionalExtremaImageFilter,

See

HMinimaImageFilter

ITK Sphinx Examples:

• All ITK Sphinx Examples

• Valued Regional Minimal Image

See itk::ValuedRegionalMinimaImageFilter for additional documentation.