[Insight-users] Create the histogram of an image

[SERIOT Rémi DEC/SPUA/LTEC]

Hi Luis,

Thanks for your help, but do you have a simple way for create the histogram
of an image ?

I found this code...may be you've got something more simple...

	itk::MinimumMaximumImageCalculator<ImageType>::Pointer
rangeCalculator = 
		itk::MinimumMaximumImageCalculator<ImageType>::New();
	rangeCalculator->SetImage( m_image );
	rangeCalculator->Compute();

	MinValue = rangeCalculator->GetMinimum();
	MaxValue = rangeCalculator->GetMaximum();

	typedef itk::Statistics::Histogram<PixelType, 1> HistogramType;
	histogram = HistogramType::New();

	HistogramType::SizeType size;
	size[0] = MaxValue;
	histogram->Initialize( size );

	for ( int ibin = 0; ibin < MaxValue - 1; ibin++ ) {
		histogram->SetBinMin( 0, ibin, ibin );
		histogram->SetBinMax( 0, ibin, ( ibin + 1 ) );
    }
	// put each image pixel into the histogram
	typedef itk::ImageRegionConstIterator<ImageType> ConstIterator;
	ConstIterator iter( m_image, m_image->GetBufferedRegion() );

	while ( !iter.IsAtEnd() ) {
		
		PixelType value = iter.Get();
		
		if ( static_cast<double>(value) >= MinValue && 
			 static_cast<double>(value) <= MaxValue ) {
      
			// add sample to histogram

			HistogramType::IndexType index;
			HistogramType::InstanceIdentifier id;
			HistogramType::MeasurementVectorType measurement;
  
			measurement[0] = value;
			index = histogram->GetIndex( measurement );
			id = histogram->GetInstanceIdentifier( index );
			histogram->IncreaseFrequency( id, 1 );
		}
		++iter;
	}

Thanks

Remi

> -----Message d'origine-----
> De : Luis Ibanez [mailto:luis . ibanez at kitware . com]
> Envoyé : mercredi 18 juin 2003 16:02
> À : SERIOT Rémi DEC/SPUA/LTEC
> Cc : 'Joshua Cates'; 'insight-users at public . kitware . com'; Jisung Kim
> Objet : Re: [Insight-users] Sorting watershed basins based on size
> 
> 
> 
> Hi Remi,
> 
> It sounds like you could simply compute the Histogram
> of the labeled image.
> 
> The histogram will give you the number of pixels assigned
> to each one of the labels, and since the labels are unique,
> you will get the number of pixels on each watersed basin.
> 
> You will find details on the use of the ITK histogram
> in the Statistics chapter of the SoftwareGuide.
> 
>    'insight-users at public . kitware . com'
> 
> Section 9.1.3, pdf-page 320
> 
> The associated example is available in
> 
>     Insight/Examples/Statistics/Histogram.cxx
> 
> In the same chapter you will find options for sorting.
> 
> 
> 
> Regards,
> 
> 
>     Luis
> 
> 
> -------------------------------
> SERIOT Rémi DEC/SPUA/LTEC wrote:
> > Hi,
> > 
> > I would like to sort watershed basins based on size, so I 
> need to calculate
> > the size of each basin from the labeled image. I need to do 
> that and I don't
> > wont to re-invent something already done.
> > I think that I could use a simple ImageIterator and an 
> accumulator for
> > compute the number of pixels in each basin from the labeled 
> image and then
> > sort this list for keep only the most significant basins.
> > 
> > Could I speed it up this process with
> > itk::watershed::Segmenter::flat_region_t information ?
> > 
> > Or there is another way to do the same thing ?
> > 
> > After that could I have to change the EquivalencyTable ?
> > 
> > Thanks for your help
> >  
> > Rémi
> > 
> > 
> >>-----Message d'origine-----
> >>De : Joshua Cates [mailto:cates at sci . utah . edu]
> >>Envoyé : vendredi 13 juin 2003 18:05
> >>À : SERIOT Rémi DEC/SPUA/LTEC
> >>Cc : 'insight-users at public . kitware . com'
> >>Objet : RE: [Insight-users] How to create my own 
> >>NeighborhoodOperator ?
> >>
> >>
> >>Hi Rémi,
> >>
> >>Glad to hear the NeighborhoodOperator is working out.
> >>
> >>In order to sort and merge watershed basins based on size you 
> >>will have to
> >>modify the itkWatershedSegmenter algorithm to keep track of 
> >>basin sizes.  
> >>The initial size would need to be computed in the gradient 
> >>descent step of
> >>itkWatershedSegmenter and then updated and maintained during 
> >>basin merge
> >>operations.
> >>
> >>An alternate approach of a one-time suppression of small 
> basins in the
> >>initial output might be interesting (but will result in a different
> >>algorithm and I can't guarantee you won't get some 
> >>undesirable grouping of
> >>basins).  You could calculate the basin sizes from the the initial
> >>segmentation (zero merge level output) of the 
> >>WatershedSegmenter and then
> >>use some of the existing code for basin merges (in
> >>itkWatershedSegmentTreeGenerator, for example) to pre-merge 
> >>the smaller
> >>basins in the segment tree.
> >>
> >>Josh.
> >>______________________________
> >> Josh Cates			
> >> School of Computer Science	
> >> University of Utah
> >> Email: cates at sci . utah . edu
> >> Phone: (801) 587-7697
> >> URL:   http://www . sci . utah . edu/~cates
> >>
> > 
> > _______________________________________________
> > Insight-users mailing list
> > Insight-users at www . itk . org
> > http://www . itk . org/mailman/listinfo/insight-users
> > 
> 
> 
>