[Insight-users] smothing and peaks of an histogram

[Raquel Itk]

Hi,
I have  a problem to construct a binary image. I want to segment the lung
regions of DICOM image, so I compute a gray-level histogram, and the
gray-level that maximizes the separation between the two major peaks in the
histogram is selected as the gray-level threshold to compute the binary
image.
I compute the histogram and then I smoothing because I have a lot of peaks
in this way, I transform the values of the histogram in an Image 1d (thanks
a Luis):

int * createImage(int *valoresHisto){

    //creamos la imagen 1d
    size1D.Fill( 255 );
    start1D.Fill( 0 );
    region1D.SetSize( size1D );
    region1D.SetIndex( start1D );
    line->SetRegions( region1D );
    line->Allocate();

    IteratorType lineIt(line, line->GetRequestedRegion());
    int i = 0;
    //rellenamos la imagen con los valores del histograma
    for (lineIt.GoToBegin(); !lineIt.IsAtEnd();
    ++lineIt)
    {
        lineIt.Set( valoresHisto[i]);
        i=i+1;
    }


    typedef itk::ImageFileWriter< ImageType1D > WriterType1D;
    WriterType1D::Pointer writer1D = WriterType1D::New();
    writer1D->SetFileName( "Image1D.png" );
    writer1D->SetInput( line );
    try
    {
        writer1D->Update();
    }
    catch (itk::ExceptionObject &e)
    {
        std::cerr << e << std::endl;

    }

    smoothingFilter->SetSigma( 5 );
    smoothingFilter->SetInput( line );
    smoothingFilter->Update();
    ImageType1D::Pointer image= smoothingFilter->GetOutput() ;
    ImageType1D::ConstPointer inputImage =smoothingFilter->GetOutput() ;
    ImageType1D::RegionType inputRegion =inputImage->GetBufferedRegion();
    IteratorType  iterator( image, inputRegion);

    static int valoresSuavizado[512];
    i=0;
    for (iterator = iterator.Begin(); !iterator.IsAtEnd(); ++iterator)
    {
       std::cout<< iterator.Get()<< std::endl;
        valoresSuavizado[i]=iterator.Get();
        i=i+1;
    }

    return valoresSuavizado;
}



But I have problem with the first values, because there are higher values, I
use sigma=5.
Another question is about to calculate the threshold, somebody can suggest
me how I can compute that.

Thanks a lot.
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