[Insight-users] NumericLimits::min float / int Inconsistency Workaround?

[Luis Ibanez]

Hi Geoff,

Thanks for the clarifications.

The simple option is to write your own thresholding filter.

               It is actually quite easy.


Just do the following:

A) Copy paste the files itkBinaryThresholdImageFilter. h and txx

B) Rename them, and rename the class inside.

C) Modify the .h file in lines 98-105.

    Replace:

   inline TOutput operator()( const TInput & A ) const
     {
     if ( m_LowerThreshold <= A && A <= m_UpperThreshold )
       {
       return m_InsideValue;
       }
     return m_OutsideValue;
     }

    with

   inline TOutput operator()( const TInput & A ) const
     {
     if ( m_LowerThreshold <  A  )
       {
       return m_InsideValue;
       }
     return m_OutsideValue;
     }

D) Get rid of all references to Upper threshold



    and once you get it to work,


    We encourage you to share your new filter with the community
    by submitting it to the Insight Journal

         http://www.insight-journal.org



     Regards,


         Luis



---------------------
Geoff Topping wrote:
> Hi Luis,
> 
> If I use a lower threshold of NumericTraits::Zero, voxels with value equal to 0 are set to the inside value in the output image.
> 
> Also, the comments in itkBinaryThresholdImageFilter.h say:
> 
>  * Values equal to either threshold is considered to be between the thresholds.
> 
> Geoff Topping
> 
> ----------------------------------------
> 
>>Date: Wed, 20 May 2009 22:08:52 -0400
>>From: luis.ibanez at kitware.com
>>To: g_topping at hotmail.com
>>CC: insight-users at itk.org
>>Subject: Re: [Insight-users] NumericLimits::min float / int Inconsistency Workaround?
>>
>>
>>Hi Geoff,
>>
>>If what you want is to get all values larger than zero,
>>
>>what is wrong with using:
>>
>>
>>UpperThreshold = NumericTraits::max()
>>LowerThreshold = NumericTraits::Zero
>>
>>??
>>
>>
>>Something is contradictory in your description of
>>requiremets.
>>
>>
>>
>>Luis
>>
>>
>>
>>-------------------------
>>Geoff Topping wrote:
>>
>>>Hi all,
>>>
>>>I'm trying to make an itk::BinaryThresholdImageFilter with a lower bound that includes all values larger than zero. Doing this in a generic way has proven difficult due to the inconsistency in how itk::NumericLimits reports min values for float or integer types.
>>>
>>>To clarify, this code:
>>>
>>>std::cout << "NumericTraits float min: " << itk::NumericTraits::min() << std::endl;
>>>std::cout << "NumericTraits signed short min: " << itk::NumericTraits::min() << std::endl;
>>>
>>>outputs this:
>>>
>>>NumericTraits float min: 1.17549e-38
>>>NumericTraits signed short min: -32768
>>>
>>>And since I'm working with signed short pixels, I can't use NumericTraits::min() to set the lower threshold for my filter (although I presumably could if I was using float pixel type).
>>>
>>>
>>>This issue is not unique to itk::NumericTraits, but is present in std::numeric_limits as well, for reasons that are irrelivant to this discussion.
>>>
>>>
>>>My question: Is there a reccommended ITK style workaround for this?
>>>
>>>I want to be able to set the lower-threshold for my filter in a generic way, so don't want to set it to constants 1 (integer), as that would be well above the minimum positive value for a float type pixel.
>>>
>>>I can't use NumericTraits to get the positive minimum value representable by the type, although NumericTraits seems to be the standard way of getting this sort of information in ITK code.
>>>
>>>I could use a separate thresholding step to get a mask image with NumericLimits::Zero for values between NumericLimits::NonpositiveMin and NumericLimits::Zero and NumericLimits::One outside that range, and then multiply my original image by this mask to get a nonnegative image, and then apply a separate threshold filter on that, but I shouldn't need to do those extra steps.
>>>
>>>
>>>Notably, there exist implmentations of similar functions to resolve this, including one in the Boost libraries:
>>>
>>>http://www.boost.org/doc/libs/1_38_0/libs/numeric/conversion/doc/html/boost_numericconversion/bounds___traits_class.html
>>>
>>>I'm not using any Boost code in my current programs, though.
>>>
>>>
>>>Is there a reason NumericTraits doesn't have a function to provide the value I need?
>>>
>>>NumericTraits does have a NonpositiveMin() function, for a similar purpose, which is implemented differently for float and integer types:
>>>
>>>static float NonpositiveMin() { return -vcl_numeric_limits::max(); }
>>>
>>>static int NonpositiveMin() { return vcl_numeric_limits::min(); }
>>>
>>>
>>>Thanks,
>>>Geoff Topping
>>>
>>>
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