[Insight-users] Re: scale factor in registration methods

[Silvester Czanner]

Luis,

thank you for your explanation. I tried to "play" with the example, you 
recommended me, but  I was not successful. :-(
I registered the ITK images:

[czanner@gabi test]$ ~/CVSROOT/Insight_bin/bin/ImageRegistration7 
BrainProtonDensitySliceBorder20.png BrainProtonDensitySliceR10X13Y17.png 
a.mha

here is my result:
Result =
 Scale         = -6.87933e-08
 Angle         = 1.42343e-08
 Center X      = 110.281
 Center Y      = 128.664
 Translation X = 122.5
 Translation Y = 144.5
 Iterations    = 423
 Metric value  = 21561.4

It is far away from the reality... . Could you, please recommend me some 
setup for this method, I use similar parameters as it is in other examples .

Is this ( I mean the Similarity2DTransform ) the only method, where it 
is possible to register images with different sizes ?

Thank you,
Silvester

Luis Ibanez wrote:

> Hi Silvester,
>
> Setting the optimization-scale factors for Scaling
> is even harder than for rotations.  The reason is
> that scales should in principle be treated in a
> logarithmic framework.
>
> The following example uses the Similarity Transform,
> which does Rotation, Translation and Scaling:
>
> Insight/Examples/Registration/ImageRegistration7.cxx
>
>
> You may want to keep smaller step sizes when Scale
> Factors are present in the transform, because the
> non-linearity of the scale makes the optimization
> quite unstable.
>
> This involves a laborious work of parameter
> tunning... so... don't expect it to work at the
> first try.
>
>
> Please let us know if you find any problem.
>
>    Thanks
>
>      Luis
>
> -----------------------------
> Silvester Czanner wrote:
>
>> Hi Luis,
>>
>> I am trying to use the registrations methods from ITK. The assumption 
>> is, that there will be some small rotation, shifting and also 
>> scaling. I received quite good results, when the registration images 
>> have the same size, but there is a problem with scaling factor. When 
>> I look to the examples there are use only images with shifting and 
>> rotation. Where can I find how to setup or use the scaling factor in 
>> registration?
>>
>> Thank you,
>>
>> Silvester
>>
>
>
>
>
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-- 

Silvester Czanner, PhD

Pittsburgh Supercomputing Center    | tel. +1 412 268 3496
Carnegie Mellon University          | fax  +1 412 268 5832
4400 Fifth Avenue,                  | czanner@psc.edu
Pittsburgh, PA 15213, USA           | http://www.psc.edu/~czanner

... the life would be much simpler, if we have a source code for it ...