Solution:AW: [Insight-users] Question about itk::ThresholdSegmentationLevelSetImageFilter

[jiang]

Many thanks to Luis and Joshua,
I find out why the second case doesn't work. Since I wrote the image data to
.png file some days ago, I forgot that I rescale the image data to unsigned
char type as below:

  typedef unsigned char                   VisualizationPixelType;
  typedef itk::Image< VisualizationPixelType, 2 >
VisualizationImageType;
  typedef itk::RescaleIntensityImageFilter<
                          ImageType,
                          VisualizationImageType >   RescaleIntensityFilter;

	RescaleIntensityFilter::Pointer     RescaleIntensity;

	RescaleIntensity  = RescaleIntensityFilter::New();
	RescaleIntensity->SetOutputMaximum( itk::NumericTraits<
VisualizationPixelType >::max() );
	RescaleIntensity->SetOutputMinimum( itk::NumericTraits<
VisualizationPixelType >::min() );
	RescaleIntensity->SetInput( ImageData );

Then write this RescaleIntensity->GetOutput() to .png file.
So I try to rescale image data as this procedure, then cast to float type,
then input it as filter->SetFeatureImage(). This time, the second case works
same as first case.

I'm sorry that I disturb you so much because my fault. Any way your answers
give me some help from other point of view.

Thank you again and have a nice day!


Chunyan

-----Ursprungliche Nachricht-----
Von: Joshua Cates [mailto:cates at sci.utah.edu]
Gesendet: Mittwoch, 28. Januar 2004 18:10
An: jiang
Cc: ITK
Betreff: Re: [Insight-users] Question about
itk::ThresholdSegmentationLevelSetImageFilter


Hello Chunyan,

There is probably something in the casting of your image types that is
causing the differences, but I cannot tell from your description how your
pipeline is constructed.  Note that the
ThresholdSegmenationLevelSetImageFilter will automatically cast the
FeatureImage input to a floating point type.  All of the level-set filters
requires floating point precision for correct results.  Explicitly casting
the image to float before setting it as the input should not change the
result but is not required.

Josh.

______________________________
 Josh Cates
 Scientific Computing and Imaging Institute
 University of Utah
 Email: cates at sci.utah.edu
 Phone: (801) 587-7697
 URL:   http://www.sci.utah.edu/~cates


On Wed, 28 Jan 2004, jiang wrote:

> Dear ITK-users,
> I tried to do image segmentation by
> itk::ThresholdSegmentationLevelSetImageFilter. It can work now. Firstly, I
> set m_thresholdSegmentation->SetFeatureImage() by read a .png file. Then I
> try to set m_thresholdSegmentation->SetFeatureImage() by one
> InputImageType::Pointer. But the result is not same as before. The other
> settings are totally same. The following is the detail:
> In the first case:
>    typedef signed short                    PixelType;
>    typedef itk::Image<PixelType, 2>        ImageType;
>
>    itk::PNGImageIO::Pointer io;
>    io = itk::PNGImageIO::New();
>    itk::ImageFileWriter<ImageType>::Pointer writer;
>
>    typedef   float                                   InputPixelType;
>    typedef   itk::Image< InputPixelType, 2 >         InputImageType;
>    typedef   itk::ImageFileReader<InputImageType >   ReaderType;
>    ReaderType::Pointer reader;
>
>    ImageType::Pointer --> writer("ImageFile.png") --> reader
>    m_thresholdSegmentation->SetFeatureImage(reader->GetOutput())
>
> In the second case:
>    typedef itk::CastImageFilter<ImageType,InputImageType> CasterType;
>    CasterType1::Pointer Caster;
>
>    ImageType::Pointer --> Caster
>    m_thresholdSegmentation->SetFeatureImage(Caster->GetOutput())
>
>
> The result of second case is not what I want. How can I get the same
result
> as first case, but not use "writer" and "reader", directly by Pointer?
>
>
> Thanks a lot!
>
>
> Chunyan
>
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