[Insight-users] Image Metrics on Image Regions

[Stefan Schmidt]

Hi Luis,

thank you for the quick and detailed response, that already helped me a lot.

> In typical block-matching algorithms you are
> probably looking just at translations transforms,
> (not rotations nor scale changes). That makes
> item (3) to be just the itk::TranslationTransform.

In my case (for the moment still from a very abstract point of view, 
unfortunately) I'd rather like to use a composition of two transforms, namely 
a global one (that I'm trying iteratively to estimate with my algorithm), and 
the TranslationTransform to point to the block I'm comparing with. But I 
guess I have to interpolate an intermediate image as I can't plug 2 
Transforms into the Metric, right? Alternatively, I could maybe implement a 
"composed transform" herited from the Transform class.


> You may want to prepare some coffee and evaluate both
> approaches...

Yes indeed :-)


> B)  You could use the Kernel based transforms as a
>      helper class for computing the Affine part of
>      the deformation field.
[...]
>     Once the computation is done, you will have:
>
>   - AMatrix holds the rotation+scaling part of the Affine transform
>   - BVector holds the translation part of the Affine transform

I must admit I don't fully understand this method yet, but it sounds 
interesting. 
Anyways, Rotation+scaling+translation gives only a similitude transform, what 
about the shear part, can one get that, too?


Best regards,
Stefan Schmidt