Extract Contours From Image

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Synopsis

Extract contours from an image.

Results

Note

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Code

C++

/*
#include "itkImage.h"
#include "itkImageFileWriter.h"
#include "itkSimpleContourExtractorImageFilter.h"
#include "itkImageRegionIterator.h"

using UnsignedCharImageType = itk::Image<unsigned char, 2>;

static void CreateImage(UnsignedCharImageType::Pointer image);

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

  using SimpleContourExtractorImageFilterType = itk::SimpleContourExtractorImageFilter <UnsignedCharImageType, UnsignedCharImageType>;
  SimpleContourExtractorImageFilterType::Pointer contourFilter
          = SimpleContourExtractorImageFilterType::New();
  contourFilter->SetInput(image);
  contourFilter->Update();

  using WriterType = itk::ImageFileWriter< UnsignedCharImageType  >;
  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName("output.png");
  writer->SetInput(contourFilter->GetOutput());
  writer->Update();

  return EXIT_SUCCESS;
}

void CreateImage(UnsignedCharImageType::Pointer image)
{
  // Create an image
  itk::Index<2> start;
  start.Fill(0);

  itk::Size<2> size;
  size.Fill(100);

  itk::ImageRegion<2> region(start,size);

  image->SetRegions(region);
  image->Allocate();
  image->FillBuffer(0);

  // Create a line pixels
  for(unsigned int i = 40; i < 60; ++i)
    {
    itk::Index<2> pixel;
    pixel.Fill(i);
    image->SetPixel(pixel, 255);
    }

  // Create another line of pixels
  for(unsigned int i = 10; i < 20; ++i)
    {
    itk::Index<2> pixel;
    pixel[0] = 10;
    pixel[1] = i;
    image->SetPixel(pixel, 255);
    }

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

Classes demonstrated

template<typename TInputImage, typename TOutputImage>
class SimpleContourExtractorImageFilter : public itk::BoxImageFilter<TInputImage, TOutputImage>

Computes an image of contours which will be the contour of the first image.

A pixel of the source image is considered to belong to the contour if its pixel value is equal to the input foreground value and it has in its neighborhood at least one pixel which its pixel value is equal to the input background value. The output image will have pixels which will be set to the output foreground value if they belong to the contour, otherwise they will be set to the output background value.

The neighborhood “radius” is set thanks to the radius params.

ITK Sphinx Examples:

• All ITK Sphinx Examples

• Extract Contours From Image

See

Image

See

Neighborhood

See

NeighborhoodOperator

See

NeighborhoodIterator

See itk::SimpleContourExtractorImageFilter for additional documentation.