[Insight-users] Phase correlation registration

[Jakub Bican]

Hi,

the problem is that PCM supposes that the images are periodically
extended beyond their bounds. This means that shift dX is for PCM the
same as any shift dX+k*sX where sX is the image size and k is any
integer.

In the actual code, the shift is computed from the peak using this code:

  for (int i = 0; i < ImageDimension ; i++)
    {
    if ( index[i] > vcl_floor( size[i] / 2.0 ) )
      {
      offset[i] = -1*(index[i] - size[i]) * spacing[i];
      }
    else
      {
      offset[i] = -1*index[i] * spacing[i];
      }
    }

This approach results in maximum overlap of the two images. If this is
not enough for you, you have to apply some other metric best suited
for your images. The simple and probably too expensive aproach would
be to compute PCM of the overlapped areas for the two cases and
compare the peak height.

Feel free to ask for any details or materials...

Regards,

    Jakub

PS: PCM submission has never passed IJ compilation and tests execution
- that is mainly due to problems with fftw and vnl_fft in IJ Testing
environment. I did several tries to tune the submission before i
finally gave up. I have to review the latest submission if it
corresponds to the best available version of ITK PCM code.

PSII: we have also developed a 3D translation and rotation
registration algorithm based on PCM, but the journal publication of
the method and IJ publication of ITK code is still under progress :(
(you can find some conference proceedings by searching for Cylindrical
Phase Correlation Method)


2009/2/24  <Felix.Bollenbeck at iff.fraunhofer.de>:
>
> Hello all,
>
> Im currently trying to figure out an elegant heuristic to resolve symmetry
> (i.e. direction of the shift)
> of the Phase Correlation for translation registration being implement for
> ITK.
>
> see:
>
> http://www.insight-journal.org/browse/publication/138
>
>
> has anyone come accross the symmetry problem, or know an elegant solution?
>
> Kind regards,
>
>        Felix.
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