ITK  4.9.0
Insight Segmentation and Registration Toolkit
WikiExamples/ImageProcessing/ManuallyRemovingLabels.cxx
#include "itkImage.h"
typedef itk::Image<unsigned char, 2> ImageType;
static void CreateImage(ImageType::Pointer image);
int main(int, char *[])
{
ImageType::Pointer image = ImageType::New();
CreateImage(image);
typedef itk::BinaryImageToLabelMapFilter<ImageType> BinaryImageToLabelMapFilterType;
BinaryImageToLabelMapFilterType::Pointer binaryImageToLabelMapFilter = BinaryImageToLabelMapFilterType::New();
binaryImageToLabelMapFilter->SetInput(image);
binaryImageToLabelMapFilter->Update();
// The output of this filter is an itk::LabelMap, which contains itk::LabelObject's
std::cout << "There are " << binaryImageToLabelMapFilter->GetOutput()->GetNumberOfLabelObjects() << " objects." << std::endl;
std::vector<unsigned long> labelsToRemove;
std::cout << "There are originally " << binaryImageToLabelMapFilter->GetOutput()->GetNumberOfLabelObjects() << " objects." << std::endl;
// Note: do NOT remove the labels inside the loop! The IDs are stored such that they will change when one is deleted.
// Instead, mark all of the labels to be removed first and then remove them all together.
for(unsigned int i = 0; i < binaryImageToLabelMapFilter->GetOutput()->GetNumberOfLabelObjects(); i++)
{
// Get the ith region
BinaryImageToLabelMapFilterType::OutputImageType::LabelObjectType* labelObject = binaryImageToLabelMapFilter->GetOutput()->GetNthLabelObject(i);
//std::cout << "Region " << i << " has " << labelObject->Size() << " pixels." << std::endl;
// Mark every other label to be removed
if(i%2 == 0)
{
labelsToRemove.push_back(labelObject->GetLabel());
}
}
std::cout << "Removing " << labelsToRemove.size() << " objects." << std::endl;
// Remove all regions that were marked for removal.
for(unsigned int i = 0; i < labelsToRemove.size(); ++i)
{
binaryImageToLabelMapFilter->GetOutput()->RemoveLabel(labelsToRemove[i]);
}
std::cout << "There are " << binaryImageToLabelMapFilter->GetOutput()->GetNumberOfLabelObjects()
<< " objects remaining." << std::endl;
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(start,size);
image->SetRegions(region);
image->Allocate();
image->FillBuffer(0);
// Make line of non-touching diagonal pixels
for(unsigned int i = 0; i < 20; i+=2)
{
pixel[0] = i;
pixel[1] = i;
image->SetPixel(pixel, 255);
}
}