[Insight-users] Bug in OtsuThresholdCalculator

[Adrian Friebel Work]

Hello,
I just discovered a bug in the OtsuThresholdCalculator class.

The Otsu calculator outputs a threshold of 1, if the frequencies of the 
first two bins in the histogram are zero. (Regardless of the frequencies 
of the other bins)

I tested this with an image that contains no pixel with intensity values 
of 0 and 1. The Otsu threshold is always 1. When I reset the intensity 
of one arbitrary pixel to 0 or 1, the Otsu calculator finds a reasonable 
threshold value.

Can anyone reproduce this issue?


Best regards,
Adrian.


PS: Below the pipeline I used:


typedef unsigned char CScalarPixelType;

typedef itk::Image<CScalarPixelType, 2> CScalarImageType;

typedef itk::ImageFileReader<CScalarImageType> ScalarReaderType;
typedef itk::ImageFileWriter<CScalarImageType> ScalarWriterType;

typedef itk::OtsuThresholdImageFilter<CScalarImageType, 
CScalarImageType>   OtsuThresholdImageFilterType;

ScalarReaderType::Pointer                     reader;
OtsuThresholdImageFilterType::Pointer         otsuFilter;
ScalarWriterType::Pointer                     writer;

reader = ScalarReaderType::New();
reader->SetFileName("myfile.tif");

otsuFilter = OtsuThresholdImageFilterType::New();/
/otsuFilter->SetInput(reader->GetOutput());
otsuFilter->Update();
std::cout << (int)(otsuFilter->GetThreshold()) << std::endl;

writer = ScalarWriterType::New();
writer->SetFileName("myfile_bin.tif");
writer->SetInput(otsuFilter->GetOutput());
writer->Update();
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