[Insight-users] Histogram modification - troubles with SetFrequency

[Luis Ibanez]

Hi Sacrif,

Thanks for pointing this out.

This is indeed the case,  ITK filters own their output
and they are the only ones that should change the
output objects.

This is a requirement for good-behavior when the
filters are put into a pipeline.

You are not supposed to modify the output of a
filter.

In your case, you could create a new Histogram
manually, and copy the computed elements
from the output of the Histogram that you get from
the generator.

Something similar to:

const HistogramType * histogram1 = histogramGenerator->GetOutput();

HistogramType::Pointer histogram2 = HistogramType::New();

// Add here:
// Copy lower, upper values of bins
// Copy values of numbers of bins
// Allocate size for the new historgram2
//

//
//  Now copy the recomputed values
//
HistogramType::Iterator itr2 = historgram2->Begin();
HistogramType::ConstIterator itr1 = histogram1->Begin();

while( itr1 != histogram1->End() )
  {
  *itr2 = pow(  *itr1, 2.0 )
  ++itr1;
  ++itr2;
  }


  Regards,


        Luis


--------------------------------------------------------------------------------
On Fri, Dec 4, 2009 at 3:43 AM, sacrif <markus_m at gmx.net> wrote:
>
> Hi, I finally found out what the problem is. The histogram is defined as
> const HistogramType * histogram; or HistogramType::ConstPointer histogram;
>
> However the SetFrequency method is a not const method. Therefore non of the
> 4 SetFrequency methods is applicable on it.
>
> The problem is that the GetOutput() method of the
> itk::Statistics::ScalarImageToHistogramGenerator class returns a "const
> HistogramType *" which I assign to my "const HistogramType* histogram"
> pointer. So I can only define the histogram as const. But then the
> SetFrequency would not work. (and results in the compilation error: error
> C2663: 'itk::Statistics::Histogram<TMeasurement>::SetFrequency' : 4
> overloads have no legal conversion for 'this' pointer...<--as written in my
> previous post)
>
> Is it possible that a histogram as I defined it can't be changed as soon as
> it is created? Somehow I can't imagine this is the case. But at the moment I
> can only imagine to write the values in an std::vector to proceed working on
> it.
> I would appreciate any onther advice.
>
> Thank you & kind regards
>
> --
> View this message in context: http://old.nabble.com/Histogram-modification---troubles-with-SetFrequency-tp26615939p26635812.html
> Sent from the ITK - Users mailing list archive at Nabble.com.
>
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