[ITK-users] Histogram for a double precision array

[Dženan Zukić]

Hi Dobashi,

adding this line makes the behavior independent from pixel type:
imageToHistogramFilter->SetAutoMinimumMaximum(false);

And this is because ImageToHistogramFilter's constructor has this:
if( typeid(ValueType) == typeid(signed char) || typeid(ValueType) ==
typeid(unsigned char) )
    {
    autoMinMax->Set(false);
    }
  else
    {
    autoMinMax->Set(true);
    }

Regards,
Dženan

On Thu, Jan 26, 2017 at 10:51 AM, SDobashi <dobashisuguru at gmail.com> wrote:

> Hello, everyone,
>
> I want to calculate a histogram for a double precision C-array (or
> std::vector<double>).
>
> As a simple example, I tried to calculate a histogram for the data
>
> double data[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
>
> for the range from 5 to 10 in 10 bins, and I wrote the code listed in the
> last part of this post.
>
> This code worked well for "unsined char" but not for "double".
>
> Could anyone suggest me why this could happen?
> Please tell me a proper way to calculate a histogram of the double
> precision
> array.
>
> Thanks a lot in advance,.
>
> Kind regards,
>
> # Results for "unsigned char" data and this is what I expected:
>
> Frequency = [ 1,
> 0,
> 1,
> 0,
> 1,
> 0,
> 1,
> 0,
> 1,
> 0 ]
> Frequency of 0 : (5 to 5.5) = 1
> Frequency of 1 : (5.5 to 6) = 0
> Frequency of 2 : (6 to 6.5) = 1
> Frequency of 3 : (6.5 to 7) = 0
> Frequency of 4 : (7 to 7.5) = 1
> Frequency of 5 : (7.5 to 8) = 0
> Frequency of 6 : (8 to 8.5) = 1
> Frequency of 7 : (8.5 to 9) = 0
> Frequency of 8 : (9 to 9.5) = 1
> Frequency of 9 : (9.5 to 10) = 0
> Total count 5
>
> # Results for "double" precision data:
>
> Frequency = [ 1,
> 1,
> 1,
> 1,
> 1,
> 1,
> 1,
> 1,
> 1,
> 1 ]
> Frequency of 0 : (0 to 0.9009) = 1
> Frequency of 1 : (0.9009 to 1.8018) = 1
> Frequency of 2 : (1.8018 to 2.7027) = 1
> Frequency of 3 : (2.7027 to 3.6036) = 1
> Frequency of 4 : (3.6036 to 4.5045) = 1
> Frequency of 5 : (4.5045 to 5.4054) = 1
> Frequency of 6 : (5.4054 to 6.3063) = 1
> Frequency of 7 : (6.3063 to 7.2072) = 1
> Frequency of 8 : (7.2072 to 8.1081) = 1
> Frequency of 9 : (8.1081 to 9.009) = 1
> Total count 10
>
>
> # Code I wrote:
>
> #include "itkImage.h"
> #include "itkImportImageFilter.h"
> #include "itkImageToHistogramFilter.h"
>
> using namespace std;
>
> int main(int argc, char* argv[])
> {
>     //typedef unsigned char PixelType;
>     typedef double PixelType;
>     const int Dimension = 1;
>
>     const int numElems = 10;
>     PixelType data[numElems] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
>
>     typedef itk::Image<PixelType, Dimension> ImageType;
>     typedef itk::ImportImageFilter<PixelType, Dimension> ImportFilterType;
>
>     ImportFilterType::Pointer importFilter = ImportFilterType::New();
>
>     ImportFilterType::SizeType size;
>     size[0] = numElems;
>
>     ImportFilterType::IndexType start;
>     start[0] = 0;
>
>     ImportFilterType::RegionType region;
>     region.SetIndex(start);
>     region.SetSize(size);
>
>     importFilter->SetRegion(region);
>
>     importFilter->SetImportPointer(data, numElems, false);
>
>     importFilter->Update();
>
>     ImageType::Pointer img = importFilter->GetOutput();
>
>     const unsigned int binsPerDimension = numElems;
>
>     const unsigned int MeasurementVectorSize = 1;
>
>     typedef itk::Statistics::ImageToHistogramFilter<ImageType>
> ImageToHistogramFilterType;
>
>     ImageToHistogramFilterType::HistogramType::MeasurementVectorType
> lowerBound(binsPerDimension);
>     lowerBound.Fill(5);
>
>     ImageToHistogramFilterType::HistogramType::MeasurementVectorType
> upperBound(binsPerDimension);
>     upperBound.Fill(10);
>
>     ImageToHistogramFilterType::HistogramType::SizeType
> histSize(MeasurementVectorSize);
>     histSize.Fill(binsPerDimension);
>
>     ImageToHistogramFilterType::Pointer imageToHistogramFilter =
> ImageToHistogramFilterType::New();
>     imageToHistogramFilter->SetInput(img);
>     imageToHistogramFilter->SetHistogramBinMinimum(lowerBound);
>     imageToHistogramFilter->SetHistogramBinMaximum(upperBound);
>     imageToHistogramFilter->SetHistogramSize(histSize);
>
>     try {
>         imageToHistogramFilter->Update();
>     }
>     catch (itk::ExceptionObject& error) {
>         std::cerr << "Error: " << error << std::endl;
>         return EXIT_FAILURE;
>     }
>
>     ImageToHistogramFilterType::HistogramType* histogram =
> imageToHistogramFilter->GetOutput();
>
>     std::cout << "Frequency = [ ";
>     for (unsigned int i = 0; i < histogram->GetSize()[0]; ++i) {
>         std::cout << histogram->GetFrequency(i);
>
>         if (i != histogram->GetSize()[0] - 1) {
>             std::cout << "," << std::endl;
>         }
>     }
>     std::cout << " ]" << std::endl;
>
>     for (unsigned int i = 0; i < histogram->GetSize()[0]; i++) {
>         std::cout << "Frequency of " << i << " : ("
>         << histogram->GetBinMin(0, i) << " to " << histogram->GetBinMax(0,
> i)
>         << ") = " << histogram->GetFrequency(i) << std::endl;
>     }
>
>     std::cout << "Total count " << histogram->GetTotalFrequency() <<
> std::endl;
> }
>
>
>
>
> --
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