[Insight-users] registering images from thumbnails

[Mauro Maiorca]

Kevin, thanks very much for your email

> If you used ITK to sub-sample the images, and sub-sampled and registered
> the images in the same application, or used a file type that knows about
> image spacing.... you should be able to use finalParameters as is.

yep, same application, same function.
I also tried using the finalParameters "as is" on the non-sub-sampled
(Original) image and -as expected- it didn't work (I get as result an
image filled with the default value). I suspect finalParameters should
be changed to be used on the non-sub-sampled image, but I'm not
getting how to do that.

> These parameters do not know anything about pixel spacing.

exactly!
But I know pixel spacing before and after the resampling.
The idea is -indeed- to change the "finalParameters" using the
pixel-spacing before and after the resampling. Does it make sense?

> I added all those caveats because if the pixel spacing and image origin
> are not preserved when the thumbnails were made then the translation and
> rotation would not be useful.

While you reduce the image to thumbnails, the pixel spacing have to
change (the sampling frequency is changing)!

The idea is:

*) reducing Originals to Thumbnails
*) calculate the transformation parameters (by registering)
*) "somehow" modify the transformation parameters and apply them to
the Originals.

I got troubles on figuring out the "somehow"  ;-)
Since I'm using VersorRigid3DTransform, I suspect the first 3
parameters (rotations) should stay the same, and the last 3 parameters
(translation) should be "somehow" changed. Any clue?

cheers,
Mauro