[Insight-users] NumericLimits::min float / int Inconsistency Workaround?
Bradley Lowekamp
blowekamp at mail.nih.gov
Thu May 21 09:24:39 EDT 2009
Geoff,
What about using some boolean logic.
!(NumericTraits<>::min() <= pixel <= NumericTraits<>::Zero) should be
equivalent to (NumericTraits<>::Zero < pixel)
Just use a NotImageFilter? or perhaps write a read-only
NotImageAdaptor if you prefer.
Brad
On May 21, 2009, at 12:00 AM, Geoff Topping wrote:
>
> Hi again,
>
> It seems odd to write (and thus need to test and support) a separate
> specialized NonInclusiveLowerThresholdFilter when there already is a
> more general filter that could do the job given appropriate inputs.
>
> Is there a reason NumericTraits<>::PositiveMin can't / shouldn't be
> added? This would have applications outside the scope of my
> particular problem, and is a surprising omission, to me.
>
> If PositiveMin can't be added, I'd suggest modifying
> BinaryThresholdImageFilter to take optional second parameters for
> the SetLowerThreshold and SetUpperThreshold functions. These
> parameters would be bools that indicate whether the whether the
> threshold test should include values equal to the threshold value.
> The default value would be inclusive thresholds, so as to not break
> existing code that expects the current behaviour.
>
> Alternatively, new functions named something like
> SetLowerThresholdInclusive(bool) and
> SetUpperThresholdInclusive(bool) could set whether each threshold is
> inclusive, defaulting to the current behaviour, if default
> parameters are frowned upon.
>
> Similarly, SetUpperThresholdInclusive(), SetUpperThresholdExclusive)
> and equivalents for the lower threshold could work.
>
> I don't know if there is an established precedent elsewhere in ITK
> for how such situations should be handled...
>
> Geoff
>
> ----------------------------------------
>> Date: Wed, 20 May 2009 23:41:40 -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,
>>
>> 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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========================================================
Bradley Lowekamp
Lockheed Martin Contractor for
Office of High Performance Computing and Communications
National Library of Medicine
blowekamp at mail.nih.gov
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