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

Thu May 21 10:49:43 EDT 2009

For the next release, perhaps we should add a PositiveMin trait as
Geoff suggested. I guess for non-integral types it would be: min() and
for integral types it would be 1.

I don't think it is that much work.

Bill

On Thu, May 21, 2009 at 9:24 AM, Bradley Lowekamp
<blowekamp at mail.nih.gov> wrote:
> 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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