[Insight-developers] Question regarding itkColorTable

[James Ross]

Hi Luis,

Thanks for your reply. My personal preference would be for option 1 (the 
more flexible of the two). I can plan on making the change and 
committing if there are no objections.

Regards,

-James

Luis Ibanez wrote:
> Hi James,
>
> Thanks for pointing this out.
>
> You are right this looks like a bug.
>
>
> It was probably thought for the case of "unsigned char"
> types, where "max()" will make sense.
>
>
> The following couple of options
> come to mind for fixing this issue:
>
> 1) Have member variables
>      * m_ComponentMinimum
>      * m_ComponentMaximum
>
>    that will be initialized by default in the constructor
>    to the values
>
>        NumericTraits<TPixel>::NonpositiveMin(),
>        NumericTraits<TPixel>::max())
>
>    respectively,
>
>     and that could also be set by the user via
>     SetMacro()  methods.
>
>
> OR
>
>
> 2)  Provide specialized ColorTraits<> classes
>      that will define the proper Min and Max values
>      for every type.
>
>
>
> The advantage of the first method is that it is
> more flexible.
>
> The advantage of the second method is that
> it will choose the "best" values by default.
>
>
>  What do you think of these two options ?
>
>
>
>         Thanks
>
>
>
>              Luis
>
>
>
> -----------------------------------------------------------
> On Wed, Dec 23, 2009 at 11:00 AM, James Ross <jross at bwh.harvard.edu> wrote:
>   
>> Greetings,
>>
>> I have recently been working with itkColorTable and have a question about
>> the UseRandomColors method. When I attempt the following:
>>
>> typedef itk::ColorTable< float > ColorType;
>>
>> ColorType::Pointer colorTable = ColorType::New();
>> colorTable->UseRandomColors( 5000 );
>>
>> my program crashes.
>>
>> However, if I alter the body of ::UseRandomColors from:
>>
>>   r = static_cast<TPixel>(vnl_sample_uniform(NumericTraits<TPixel>
>>                          ::NonpositiveMin(), NumericTraits<TPixel>::max()));
>>   m_Color[i].SetRed( r );
>>   g = static_cast<TPixel>(vnl_sample_uniform(NumericTraits<TPixel>
>>                          ::NonpositiveMin(), NumericTraits<TPixel>::max()));
>>   m_Color[i].SetGreen( g );
>>   b = static_cast<TPixel>(vnl_sample_uniform(NumericTraits<TPixel>
>>                          ::NonpositiveMin(), NumericTraits<TPixel>::max()));
>>   m_Color[i].SetBlue( b );
>>
>> to:
>>
>>   r = static_cast<TPixel>( vnl_sample_uniform( 0.0, 1.0 ) );
>>   m_Color[i].SetRed( r );
>>   g = static_cast<TPixel>( vnl_sample_uniform( 0.0, 1.0 ) );
>>   m_Color[i].SetGreen( g );
>>   b = static_cast<TPixel>( vnl_sample_uniform( 0.0, 1.0 ) );
>>   m_Color[i].SetBlue( b );
>>
>> my program runs, and I get expected behavior. Why are the color components
>> randomly chosen in the interval from non-positive min to max in the
>> original? Isn't the floating point color component convention associated
>> with the interval [0.0, 1.0]?  If the original is a logical bug, I'd be
>> happy to fix and commit. If I'm doing something incorrectly, please let me
>> know.
>>
>> Many thanks,
>>
>> -James
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