[Insight-users] Fixed and moving images in translation registration method example?

[motes motes]

In the image registration examples folder there is the file:

ImageRegistration1.cxx

which performs a registration using a translation transform.

As fixed image I use:

      BrainProtonDensitySliceBorder20.png";

and as moving image I use:

      BrainProtonDensitySliceShifted13x17y.png";

located in InsightToolkit-3.12.0\Examples\Data. They look like this:

http://37133.vs.webtropia.com/apache2-default/test/translate.jpg

The resulting parameters are:

Translation X = 12.9959
Translation Y = 17.0001

But should the result not be:

Translation X = 12.9959
Translation Y = -17.0001

?

Based on the itkSoftwareGuide the transform maps from the fixed image
to the moving image. The black circle represents a point in the
fixed image:

black_circle = (x,y)

now to get to the corresponding point, marked with a red_circle, in
the moving image (direction of the transform) one needs to do:

red_circle = (x+12.9959, y-17.0001)

and NOT:

red_circle = (x+12.9959, y+17.0001)

In my twisted world the correct parameters should therefore be:

Translation X = 12.9959
Translation Y = -17.0001


I know this is extremly basic but for some reason I still don't understand this.


In the itkSoftwareGuide page 321 it actually looks correct, but its
not how the images look in the \Examples\Data folder - even more
confusing.

Hope someone can clarify this.