[Insight-users] problem in rescaling while using itkMinimumMaximumImageCalculator

[john smith]

Hello to all,

I am using an itkExtractImageFilter, an itkRescaleIntensityImageFilter and
an itkMinimumMaximumImageCalculator.With my code I want to read a 3D volume,
get a 2D slice, rescale it and then diplay this slice. But If the maximum
pixel value of the image is up to 255, then I want to rescale between
[0,255]. But if the maximum pixel value(value_max) is less than 255 then I
want to rescale my image between [0,value_max].I am using the 3D image
(MRI-crop-original.gipl, itk-snap's free data) as input and I am extracting
the first slice. This slice has value_max=122, so I should rescale it
between [0,value_max]. But when I am running my program I get the result
image (z.png) rescaled between [0,255].
 I think that my problem is that when using the
itkMinimumMaximumImageCalculator, I do not get tthe right values
[value_min,value_max]=[0,122], but I am taking these values
[value_min,value_max]=[255,0] and I think that there must be some mistake.
Also, I think that the itkExtractImageFilter, make the rescale of my image
between [0,255].Is this right? I hope somebody could help
Thanks in advance

  typedef unsigned char InputPixelType;
typedef unsigned char OutputPixelType;
typedef itk::Image< InputPixelType, 3 > InputImageType;
typedef itk::Image< OutputPixelType, 2 > OutputImageType;

typedef itk::ImageFileReader< InputImageType > ReaderType;
typedef itk::ImageFileWriter< OutputImageType > WriterType;

typedef itk::ExtractImageFilter< InputImageType, OutputImageType >
FilterType;
  FilterType::Pointer filter = FilterType::New();

   typedef itk::RescaleIntensityImageFilter< OutputImageType,
OutputImageType >    FilterType_rescale;

   typedef itk::MinimumMaximumImageCalculator <OutputImageType>
          ImageCalculatorFilterType;


 ReaderType::Pointer reader = ReaderType::New();
  WriterType::Pointer writer = WriterType::New();

    reader->SetFileName( fileName.toStdString()   );
  writer->SetFileName( "z.png" );

    reader->Update();
  InputImageType::RegionType inputRegion =
           reader->GetOutput()->GetLargestPossibleRegion();

    InputImageType::SizeType size = inputRegion.GetSize();
  size[2] = 0;

   InputImageType::IndexType start = inputRegion.GetIndex();
  ui->verticalScrollBar_z->setRange(1,size_z);
  unsigned int sliceNumber = ui->verticalScrollBar_z->value();
  start[2] = 0;

    InputImageType::RegionType desiredRegion;
  desiredRegion.SetSize(  size  );
  desiredRegion.SetIndex( start );

    filter->SetExtractionRegion( desiredRegion );

    filter->SetInput( reader->GetOutput() );
    filter->Update();

 ImageCalculatorFilterType::Pointer imageCalculatorFilter
          = ImageCalculatorFilterType::New ();
  imageCalculatorFilter->SetImage(filter->GetOutput());


  int  value_max =  imageCalculatorFilter->GetMaximum();
  int  value_min =  imageCalculatorFilter->GetMinimum();

     ui->label_20->setText(QString("max_value:%1").arg(value_max));
    ui->label_21->setText(QString("min_value:%1").arg(value_min));


    FilterType_rescale::Pointer filter_rescale = FilterType_rescale::New();
    filter_rescale->SetOutputMinimum(   0 );
    filter_rescale->SetOutputMaximum( value_max);


      filter_rescale->SetInput( filter->GetOutput() );
       writer->SetInput( filter_rescale->GetOutput() );
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