[Insight-users] Getting unknown amount random Pixels

[Luis Ibanez]

Hi Neilson,

Yes, that's my mistake, itkSetMacro() and itkGetMacro()
should only be used in classes deriving from itk::Object.


Please write the full Get/Set methods as


   PixelType GetThreshold() const
                   { return m_Threshold; }


   void      SetThreshold( PixelType value )
                   { m_Threshold = value; }



Sorry about that,


    Regards,



       Luis



-------------------------------
N.E. Mackenzie Mackay wrote:
> Hey Luis,
> 
>     Thanks for the help.  This certainly helps.
> 
>     One question.  When trying to compile itkSetMacro( Threshold,  
> PixelType ) and itkGetMacro( Threshold, PixelType ) I get a error:
> 
>      " 'GetDebug': is not a member of  
> 'ImageRandomConditionalIteratorWithIndex<class itk::Image<float,3>' "
> 
>     I am assuming this because the GetDebug method is in itkObject.h 
> which  is not inherited by ImageRandomConditionalIteratorWithIndex.  
> What  would you recommend in getting around this problem?
> 
> Thank you again,
> Neilson
> On Sep 12, 2004, at 5:19 PM, Luis Ibanez wrote:
> 
>>
>>
>> Hi Neilson,
>>
>>
>> You can easily overcome this difficulty by taking the code of the
>> Iterator, renaming the class and adding to it the functionality
>> you need for evaluating the threshold.
>>
>>
>> Please do the following:
>>
>>
>> 1) Take the files
>>
>>
>>    Insight/Code/Common
>>
>>       itkImageRandomConstIteratorWithIndex.h
>>       itkImageRandomConstIteratorWithIndex.txx
>>
>>    and rename them as
>>
>>       itkImageRandomConditionalConstIteratorWithIndex.h
>>       itkImageRandomConditionalConstIteratorWithIndex.txx
>>
>>
>>
>>
>> 2) Edit both new files and replace all occurrences of the string
>>
>>       ImageRandomConstIteratorWithIndex
>>
>> with
>>
>>       ImageRandomConditionalConstIteratorWithIndex
>>
>>
>>
>>
>>
>> 3) At the end of the header file (extension .h) just below the line
>>
>>         unsigned long  m_NumberOfPixelsInRegion;
>>
>>     add a new member variable
>>
>>         IndexType   m_Threshold;
>>
>>
>> 4)   In the current  method  Operator++()
>>
>>  Self & operator++()
>>  {
>>    this->RandomJump();
>>    m_NumberOfSamplesDone++;
>>    return *this;
>>  }
>>
>> add the following the condition for checking the
>> pixel value against the threshold
>>
>>  Self & operator++()
>>  {
>>    do {
>>       this->RandomJump();
>>       }  while( this->Get() < m_Threshold );
>>     m_NumberOfSamplesDone++;
>>     return *this;
>>  }
>>
>>
>>
>>  With this change, every time to increment the iterator, it will
>>  keep picking random samples until it finds one with value
>>  above the threshold that you set.
>>
>>   NOTE This may take significant time if the pixels with values
>>   over the threshold are not very abundant in your image.
>>
>>
>>
>> 5) Add the Set/Get methods for the Threshold by
>>   inserting lines
>>
>>
>>      itkSetMacro( Threshold, PixelType );
>>      itkGetMacro( Threshold, PixelType );
>>
>>
>>
>>   6) Then in your code instantiate this new Iterator
>>
>>
>>  typedef ImageRandomConditionalConstIreratorWithIndex<ImageType>  
>> RandomIterator;
>>
>>  RandomIterator randIter( M_FixedImage, this->GetFixedImageRegion());
>>
>>  randIter.SetNumberOfSamples( TheNumberOfSamplesThatIReallyWantToGet );
>>
>>  randIter.SetThreshold( ThisIsMyThresholdForSelectingPixels );
>>
>>  randIter.GoToBegin();
>>
>>  // this is just in case you want to put them in an array....    
>> std::vector<PixelType> myRandomPixelValuesOverThreshold;
>>
>>  do {
>>     ++randIter;
>>     myRandomPixelValuesOverThreshold.push_back( randIter.Get() );
>>   } while( !randIter.IsAtEnd() );
>>
>>
>> // At this point, the STL::Vector container has a list of // 
>> grayscale  values selected from randomly distributed
>> // pixels, all of which have values over the threshold.
>>
>>
>>
>>
>> You should read the Chapter on Image
>> Iterators from the ITK Software Guide.
>>
>>
>>    http://www.itk.org/ItkSoftwareGuide.pdf
>>
>>
>>
>>
>>
>>
>> Regards,
>>
>>
>>
>>     Luis
>>
>>
>> ----------------------------
>>
>>> ---------------------------------------------------------------------- 
>>> -- 
>>>
>>> Hi,
>>>
>>>     I am currently trying to get a set of N number of Pixels in a 
>>> image  in random locations over a set threshold.  I was attempting to 
>>> use  ImageRandomConstIteratorWithIndex but have come to realize that 
>>> you  need to set the number of samples you will be using before 
>>> starting  the iterator.  My problems is I don't know how many pixels 
>>> I need to  sample before getting N pixels over the threshold.
>>>
>>> Here is my code:
>>>
>>>     typedef ImageRandomConstIreratorWithIndex<ImageType> RandomIterator;
>>>     RandomIterator randIter( M_FixedImage, this->GetFixedImageRegion())
>>>
>>>     randIter.SetNumberOfSamples( m_NumberOfSpatialSamples );
>>>     randIter.GoToBegin();
>>>
>>>     RandomIterator ::PixelType pixelValue;
>>>     
>>>     for(int i = 0; i< N; i++)
>>>     {
>>>         pixelValue = randIter.Get();
>>>        
>>>         while(PixelValue == 0)
>>>         {
>>>             ++randIter;
>>>             pixelValue = randIter.Get();
>>>         }
>>>         printf("pixel value = %e \n", pixelValue);
>>>
>>>         container[i] = pixelValue;
>>>     }
>>>
>>>     The stuff that is printed to the screen is something like 8.61e-304
>>>
>>> Even when I simply try to use "get" some strange number comes out.   
>>> Is it because get doesn't return a float or double but a object of  
>>> some kind of container?
>>>
>>> Neilson
>>>
>>>
>>> ---------------------------------------------------------------------- 
>>> -- 
>>
>>
>>
>>
>>
> 
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