Can LabelImageToStatisticsLabelMapFilter yield invalid statistics for some labels?

grothausmann.roman · February 20, 2018, 9:56am

Hello,

LabelStatisticsImageFilter has a ValidLabelValuesContainerType where as
LabelImageToStatisticsLabelMapFilter has not. To my understanding LabelImageToStatisticsLabelMapFilter only incorporates LabelMapToLabelImageFilter in addion to LabelStatisticsImageFilter, so I’m wondering why ValidLabelValuesContainerType is missing there and whether that is critical concerning the use of any statistic values calculated by the filter.
I’m using GetNthLabelObject to iterate over the labels:

github.com

romangrothausmann/ITK-CLIs/blob/eb55ce4/label_stats.cxx

////program for itkLabelStatisticsImageFilter
//01: based on template_2inputs.cxx and analyse_labels.cxx


#include "itkFilterWatcher.h"
#include <itkImageFileReader.h>
#include <itkLabelImageToStatisticsLabelMapFilter.h>
#include <itkStatisticsLabelObject.h>
#include <itkLabelMap.h>



template<typename InputComponent1, typename TypeInputComponentType2, typename InputPixelType1, typename InputPixelType2, size_t Dimension>
int DoIt(int argc, char *argv[]){

    typedef itk::Image<InputPixelType1, Dimension>  InputImageType1;
    typedef itk::Image<InputPixelType2, Dimension>  InputImageType2;


    typedef itk::ImageFileReader<InputImageType1> ReaderType1;

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Can some labels have incorrect statistic values?

Thanks for any feedback.
Roman

blowekamp · February 20, 2018, 3:08pm

Hello Roman,

You are looking at the wrong filter.

The LabelImageToStatisticsLabelMapFilter a wrapper for a composite pipeline of LabelMapToLabelImageFilter and StatisticsLabelMapFilter. These filters are from the LabelMap module, while the StatisticsImageFilter is computed directly on a pair or traditional itk::Images.

grothausmann.roman · February 21, 2018, 10:05am

Hallo Brad,

Thanks for your reply. I’m not referring to the StatisticsImageFilter but to the LabelImageToStatisticsLabelMapFilter which seems to lack the ValidLabelValuesContainerType that the LabelStatisticsImageFilter has. Since LabelImageToStatisticsLabelMapFilter is a composition (giving statistics for each label) I would expect ValidLabelValuesContainerType unless it is somehow wrapped by the GetNthLabelObject. As I understand it, both LabelImageToStatisticsLabelMapFilter and LabelStatisticsImageFilter give statistics for each label concerning the underlying scalar-image.

blowekamp · February 21, 2018, 2:19pm

This is very confusing and I miss spoke before. I had the correct link but incorrect name! I have corrected the prior post now.

There are traditionally there Image and Image as labels. Under these concepts are the StatisticsImageFilter and the ( which you are referencing ) LabelStatisticsImageFilter.

There was introduced a new data structure called a LabelMap which is not an array of pixels but a map of label ids to run-length-encoded labels with associated data. There an MANY filters in the module with MANY composite filters. The filter you are inquiring about LabelImageToStatisticsLabelMapFilter utilize the LabelMap which has the separate interface to determine which labels are in the LabelMap. With methods such as GeNthLabelObject and GetLabels.

grothausmann.roman · February 21, 2018, 4:29pm

Many thanks Brad for that clarification.
So to make sure I understand correctly: Using GeNthLabelObject with LabelImageToStatisticsLabelMapFilter will ensure that all statistic for any reported label will be valid?
I.e. iterating over ValidLabelValuesContainerType (as in this example) is just a (very) different name for iteration over GetNumberOfLabelObjects using GeNthLabelObject in LabelImageToStatisticsLabelMapFilter (as in my code)?